Thermoplastic polymer material

FIELD: polymer materials.

SUBSTANCE: invention relates to compositions of polymer materials, which can be used to mold cutouts, fibers, tubes, films, and insulating coating on electric cable. Thermoplastic polymer material comprises polyolefin and additive for improving extrusion processing in amounts from 0.001 to 10 wt parts per 100 wt parts material. Additive is block copolymer based on diisocyanates with softening temperature below thermoplastic molding temperature.

EFFECT: improved appearance and mechanic characteristics and reduced price of manufactured products.

4 cl, 8 dwg, 1 tbl, 4 ex

 

The invention relates to compositions of polymeric materials, including organic additives to improve molding, extrusion, and specifically to compositions based on polyolefins, in particular polyethylene, with the addition of block copolymers. The invention can be used in forming the polymer profile, the insulating coating of the electric cable, plastic fiber, plastic pipes and polymer film obtained by inflating the tube.

Examples of polyolefins include, but are not limited to polymers and copolymers of ethylene, propylene, butene, pentene, hexene, and mixtures of these polymers. The invention, with some restrictions, can be used to improve the extrusion fluorinated polyolefins and blends of polyolefins with raw elastomers and peroxides, which are vulcanized by free-radical mechanism. Practically preferred materials are the polyolefins and their copolymers, obtained using metallocene catalysts. Polyolefins made with metallocene catalysts, are characterized by a narrow distribution of molecular weight polymer chains, high strength, rigidity, transparency and ease, but during extrusion acquire surface defects known as "shark" or "snake" skin, "robiniella". The occurrence of defects on the surface of the product limits the speed of processing plastics.

The most common in the industry of plastic is polyethylene. The polyethylene obtained by metallocene catalysts, replacing the conventional linear low-density polyethylene market films. According to experts in perspective 2010 world using a linear low-density polyethylene obtained by metallocene catalysts, will increase to 17 million metric tons per year and will reach about half of the total consumption of this type of plastic (Wetpanties, Nov. The production of plastics based on metallocene catalysts. Institute of petrochemical synthesis named. Aviophobia. - Plastic masses, 2001, №4 [1]). Polyethylene is used primarily for the production of the film (about 60% of the total) by extrusion and blow pipes. During extrusion of polyethylene with a narrow distribution of molecular weight already at low extrusion speeds (about 10 mm/sec) pipe surface becomes rough, and the resulting inflation tube thin film has a lower surface for reflection and scatters light passing that reduces consumer product quality. An increasing number of polyethylene, polypropylene and their copolymers are used for the manufacture of polimerov the fiber. During extrusion of the fibers through the die plate surface can buy roughness, as during extrusion of the film. The surface roughness of the fiber reduces its strength.

There are several methods of removing surface roughness during extrusion of polyolefins, namely:

- increasing the temperature of the melt;

local heating or cooling of the walls of the nozzle (tip) of the extruder;

- change the geometry of the nozzle (tip) press extruder;

- manufacturing of the nozzle (tip) of materials that increases or decreases the adhesion to the walls, the application of appropriate coatings or use of such inserts;

- the use of additives that reduce the sticking of thermoplastic material to the walls.

Increasing the melt temperature of the polyethylene in the manufacture of plastic film increases the instability of the bubble to inflate with compressed gas and leads to non-uniform film thickness, which is unacceptable in production. Additionally, increasing the temperature of the melt polymer material causes thermal decomposition, coloring material and loss of mechanical strength.

Heat output section of the mouthpiece substantially above the melting temperature of the polymer material (US Patent No. 6124428; Schmieg Joel Edward et al.; September 26, 2000, "Method of processing polyethylene and polyethylene/elastomer blends", US CL is SS: 528/487, MCI: 08 To 005/42; C 08 L 023/04 [2]; U.S. Patent No. 4485062; James W. Dawes, et al.; November 27, 1984, "Process for extruding polymers", US Class: 264/173 .19; MCI: 29 B F 003/06 [3]) or local cooling (US Patent No. 5,089,200; Chapman Jr.; et al.; February 18, 1992, "Process for melt extrusion of polymers", US Class: 264/127, MKI: 29 047/94 [4]) complicate the design of the mouthpiece.

Change the geometry of the mouthpiece may be either the increase in the thickness of the gap along the entire length of the mouthpiece (US Patent No. 5008056; Kurtz Stuart J., et al.; April 16, 1991 "Reduction in die drool in filled resins and product improvement", US Class: 264/130, MKI: 29 047/12 [5]), or a local increase of the gap near the output section of the mouthpiece (US. Patent No. 4484883; Honda; Yukio, et al.; November 27, 1984, "Multi-layer extrusion die", US Class: 425/462 MCI: 29 B F 003/08 [6]; US Patent No. 4769418; Hajime Mizuno et al.; September 6, 1988, "Propylene polymer film", US Class: 525/106, MKI: C 08 F 006/02; C 08 F 297/02 [7]), or elongation of the mouthpiece. With the increase of gap degree inflating tubes for the manufacture of a thin film is increased, and, consequently, increases the degree of orientation of the molecules of the polyethylene, resulting in reduced mechanical homogeneity of the film and the resistance of the film against wear and tear. Thicker pipe wall at the same time requires more time for cooling, which reduces the productivity of machines. The longer the mouthpiece requires a higher pressure for forcing molten thermoplastic material, which complicates and increases the cost of construction of the press ex-truder.

Manufacture of mouthpiece of the Mat is rials with a low adhesion to the polymer melt, for example, by coating the surface of the fluorinated polymers, provides increased velocity defect-free extrusion 3-5 times (Kissi et al., "Effect of surface properties on polymer melt slip and extrusion defects", Journal of Non-Newtonian Fluid Mechanics, 52 (1994) 249-261 [8]). The idea to make the mouthpiece or coating the surface of the mouthpiece of the materials, increasing the adhesion of the polyethylene to the walls, was proposed in (http://www.dowcorning.com/content/plastics/default.asp [9] and US Patent No. 4692379; Keung Jay K., et al, September 8, 1987 "Heat scalable film and method for its preparation", US Class: 428/349 MCI: 32 027/00 [10]). As an example, the implementation was given to the improvement of the quality of a film of polyethylene obtained by using a mouthpiece of brass or Nickel doped with phosphorus. However, as was subsequently shown to work V.G.Ghanta, B.L.Riise, M.M.Denn, "Disappearance of extrusion instabilities in brass capillary dies", J. Rheol., 43 (1999) 435-44 [11], the molten polyethylene glides along the brass, and does not stick to it. Additionally, the manufacture of mouthpiece made from soft materials impractical.

The industry uses additives fluorinated polymers (US Patent No. 3125547; Phillip Strubing Blatz; Mar. 17, 1964, "Extrudable composition consisting of a face and a fluorocarbon polymer" [12]), Viton® FreeFlow™" Du Pont (http://www.dupont-dow.com/products/vitonff/vitonff.asp [13],"DYNAMAR" Dyneon (3M) (http://cms.3m.com/ [14]),"KYNAR" Atofina Chemicals (http://cms.3m.com/ [15]), which are deposited on the surface of the mouthpiece during extrusion and provide sliding along the metal melt on top of the spine, or combination of such fluorinated polymers with other additives, for example, powder "dry lubricant" - BN (US Patent Application No. 20010048179, C.W. Stewart, et al., "Extrusion aid combination", December 6, 2001, US Current Class: 264/211, MKI: 29 047/00 [16]). Fluorinated polymers of the road, their use increases the cost of raw materials and also makes the connection film welding in the heat. The required amount of additives and raw material cost increases significantly in the case of extrusion of polyethylene with inorganic pigments and antiblooming additives. In addition to the fluorinated hydrocarbon to obtain a defect-free product use additives of surface - active substances (surfactants, salts and esters of fatty acids) (US Patent Application No. 20020063359, J.B.Williams, et al., "Melt processing additives for extrusion of polymers", May 30, 2002, US Class: 264/211, MKI: 08 To 005/09 [17]). The disadvantage of these technical solutions is the lack of speed defect-free extrusion process.

Know the use of the block copolymer polysiloxanes and polyurethanes (TPSU), and three block copolymer polycaprolactone and polysiloxane (TPCL-S) as additives in the extrusion of polypropylene and polyethylene (E.Yilgor, S.Suzer, I.Yilgor, "Modification of Polyolefins with Silicone Copolymers. I. Processing behavior of PP and HDPE blended with Silicone Copolymers", Journal of Applied Polymer Science, 83 (2002) 1625-1634 [18]), where it is noted that when using such additives in an amount up to 5% of the output of extrude is and at a constant force of rotation increases from 81 to 200 g/min for TSU and from 81 to 180 g/min for TPCL-S. About the defects on the surface of the product when using additives have been reported.

Summarizing the analysis of the analogies of the proposed technical solutions, we can say that so far not known cheap additives for thermoplastic polymeric material based on polyolefins, which allows to significantly increase the speed of defect-free extrusion, particularly during extrusion of compositions containing inorganic abrasive particles.

Closest to the proposed solution is a thermoplastic material with additives siloxanes with the structure of a linear diblock copolymer in combination with organophosphorus compounds (US Patent No. 4925890; Leung Pak, S., et al.; May 15, 1990, "Process for processing thermoplastic polymers", US. Class: 524/133, MKI: C 08 L 053/00 [19]), which are characterized by a higher adhesion to the material of the mouthpiece than the polymeric material. Additives are deposited on the surface of the mouthpiece and replace the main component so that the surface layer is formed additives.

The claimed invention is directed to reduction of the composition of a thermoplastic material increase in the speed of extrusion, the improvement of the appearance and mechanical characteristics of the products.

The above results are achieved by the fact that thermoplastic polymeric material comprises as the main component of the polyolefin, and the number is e from 0.001 to 10 parts by weight of on 100 parts by weight of thermoplastic polymer material additive to improve the processing of extrusion of the material in this Supplement is a block-copolymer-based diisocyanates with a softening temperature below the molding temperature of thermoplastic.

The above results are achieved also by the fact that the additive is present in an amount of from 0.01 to 1 parts by weight per 100 parts by weight of thermoplastic polymer material.

These results are achieved because of the block-copolymer-based diisocyanates is a block copolymer, based on aromatic diisocyanates.

These results are achieved because of the block copolymers on the basis of diisocyanates is a block copolymer of polyurethane with simple or complex polyester.

Terminology

The term "thermoplastic polymer material" means material containing as a main component polymers that soften and become plastic properties when heated to a temperature less than the temperature of thermal decomposition. Thermoplastic polymeric material may contain antioxidants, stabilizers, which inhibit the action of ultraviolet radiation or heat, additives to reduce static electricity, organic and inorganic fillers, dyes, is plastificator, additives that prevent the adhesion of polymeric products, such as antirakovye additives for polymer films (including silica particles, diatomaceous earth and talc), additives that improve the processing of polymers, organic dyes and inorganic pigments, the centers of crystallization of the polymer material, additives which provide the strength of brittle polymers, shocks, etc.

Any polymeric material at a temperature above the glass transition temperature exhibits elastic properties for short processes and plastic properties for long-running processes. To measure the ratio between plastic and elastic deformation and to determine the dynamic properties of the material it is deformed periodically, namely, impose a sinusoidal varying load (Austomer, Arioglu. Physics in the world of polymers. M.: Nauka, 1989 [20] and Austomer, Arioglu. Statistical physics of polymers. M.: Nauka, 1989 [21]).

If F is the force applied to the surface S in the direction parallel to this surface, the shear stress σ=F/S. Then the shear deformation γ=γo·SIN(ωt). The shear stress in the viscoelastic material is usually described with the help of G' is the elastic modulus and G" is the viscous modulus. Then σ=σabout·(G'·SIN(ωt)+G"·COS((ωt).

Figure 1 graphically presents the temperature 165° With the change of the elastic modulus G' and viscous modulus G" with frequency of exposure f=ω/2π for linear polyethylene LL1201 XV, which we used in the examples of implementation of the proposed technical solutions. Mechanical properties of polyethylene were measured with the help of the device "Rheotest RT-20" manufactured by HAAKE-Thermo. The curves intersect at a frequency of about 7 Hz. In the limit of small frequencies the effects of viscous modulus greater elastic modulus, that is, the material behaves like a liquid. In the limit of high frequencies, the effects of viscous modulus less than the elastic modulus, i.e., the material behaves as a rigid body. The ratio of the elastic modulus to a viscous modulus (G'/G") can be used as a criterion of elasticity of the material.

For molding thermoplastic polymeric materials used equipment, mainly made of metal, for example, cigarette holders, dies, pipe, casing and screws of the extruder. Commonly used metals include tool and alloy steel, stainless steel, bronze, copper, Nickel. Additionally, the metal surface may have a coating to reduce abrasive wear and corrosion, for example, electroplating of chromium, platinum and rhodium. The polymeric material is fed to the input of the equipment for forming, for example, in the form of granules, and comes out in the form of a profile, pipe, fiber, sheet is so

The molecules of the polymers can be attached to the surface through covalent bonds, hydrogen bonds and ionic bonds. Hydrogen bond is the attraction of a hydrogen atom, which is associated with electronegative atom in the same molecule to electronegative atoms in another molecule. Nonpolar molecules polyolefins are attached to the surface through covalent bonds. Block copolymers comprising at least one hard segment with the polar groups are bound to the surface via strong hydrogen bonds.

In simple copolymer of monomers of two types are mixed in the mess or alternate. In the block copolymer of monomers of the same type are connected in a long chain, and a chain of two or more monomers are connected by ends. The copolymers can exhibit quite different properties with the same chemical composition but different mutual arrangement of the monomers. Block copolymers with one hard block are used as surfactants for the preparation of suspensions and emulsions. Block copolymers with two (or more) hard blocks mainly used as thermoplastic elastomers (TPE or thermoplastic rubber and adhesives. In such systems, the hard segments are grouped together into microphases (domains) in the environment of the soft segments such as micelles in the emulsion. The connection of the hard segment is found in microphase works as a physical link to the soft segments of the polymer chain and provides the elasticity of the material. At elevated temperatures microphases (domains) of the rigid segments are softened, allowing you to process thermoplastic elastomer like a conventional thermoplastic material. However, with a small excess of the softening temperature of the hard segments, the hard segments are held together (in the micelle) due to incompatibility with soft segments, which increases the ratio of the elastic modulus to the viscous module for TPE compared with similar polymers. With further increase in temperature of the micelles disintegrate. Block copolymers with blocks more than two can have a linear structure or the structure of the graft copolymer, when soft polymer grafted hard segments.

Historically, the polyurethanes were first block copolymers, and now it is the biggest and fastest growing market segment block copolymers. Polyurethane block copolymers composed of hard and soft segments. The soft segments of the polyurethane is simple and polyesters, or polyole with a molecular weight of from 500 to 5000 AU Hard segments are aromatic or aliphatic diisocyanates in connection with low-molecular dilem or diamine. The combination of the soft and hard segments form a block-copolymer of the type (AB)nwhere n>1. Polyurethanes are two-phase domain structure due to chemical incompatibility between the soft and hard segments.

In the case of polyurethane hard segments are combined into a semi-crystalline domains, and soft segments form the amorphous matrix around. Phase separation between segments and elastic properties of block copolymers are manifested in that case, if the proportion of the soft segments is greater than the proportion of hard segments in the block copolymer is improved by increasing the share of soft segments and the increase in their molecular weight. The Association of the hard segments in microdomain provides the physical connection between the molecules. In addition to the physical connections between molecules polyurethanes possess strong hydrogen bonds. The softening temperature of the polyurethane block copolymers varied over a wide range by the choice of the hard segments. Properties of polyurethane elastomers and their chemical structure is described in detail in the technical literature, for example A.Noshay, J.E.McGrath, Block Copolymers: Overview and Critical Survey, Academic Press, New York, 1977 [22] and G.Oertel, Ed., Polyurethane Handbook, 2nd Edit., Hanser, New York, 1993 [23]).

In the processing of thermoplastic polymers are widely used lubricants and additives to improve processing of thermoplastic polymeric material by extrusion. Additives to improve processing by extrusion using, for example, to accelerate the melting of the particles of polyvinyl chloride (PVC) in the extruder and improve the homogeneity of the melt. The acceleration of melting due to the led is the group of heating the polymer mixture by eliminating slip polymeric material in the extruder, while lubricant additives provide a slide.

To improve the impact strength of brittle polymers used additives block copolymers containing soft segments that are not compatible with the polymer matrix, and the hard segments that are compatible with the matrix. Soft segments are typically characterized by a glass transition temperature below room temperature, and the hard segments are characterized by a melting temperature (glass transition) above room temperature. When mixing the additives with the molten polymer matrix soft segments are grouped into droplets with sizes from 50 to 1000 nm, and the hard segments form the shell, coupled with the polymer matrix. I believe that at room temperature the hard shell passes the elastic energy shock in elastic and soft core, where the energy is absorbed and converted into heat. The elastic properties of the core is improved, and the required amount of additives in polymer compositions decreases with increasing molecular weight and increasing the share of soft segments in relation to the hard segments.

As shown below in example 1, in the extrusion of molten polyethylene at a temperature of 165°To have surface defects with a frequency of about 20 Hz. The frequency of occurrence of defects is little change when the geometry of the molding and mainly depends on the temperature molded who I am. Without assuming theory, the probable cause of the occurrence of defects can be explained as follows. It is known that after exiting the mouthpiece surface layer of polymeric material is stretched, because of the friction of its speed inside the mouthpiece was small, and after the release it is aligned to the average flow value, i.e. the surface layer is accelerated. Stretching of the surface layer after exiting the mouthpiece leads to decrease of its thickness and instability of the separation point of the flow from the surface of the mouthpiece, so that the point of separation from the wall can move inside the mouthpiece. The occurrence of defects on the surface of the polymer material during the extrusion process can be explained as a manifestation of elastic vibrations of the material, in which there is separation of the flow from the wall of the mouthpiece near its release (loss of adhesion). This gap extends in the form of microcracks inside the mouthpiece along its walls. Thread the elastic energy of the deformed surface layer to the tip of the microcrack accelerates its progression. Then the crack deviates from the surface and breaks the polymer material (loss of cohesion). The deviation of the crack from the wall may be due to the instability of the rectilinear propagation of cracks at high speeds, as well as the fact that the surface layer of the polymer material begins astagiudiziaria inside the mouthpiece near the exit, and crack is deflected toward the source of elastic energy. Micrometry in the surface layer of polymer material, which occurred inside the mouthpiece is moved in the extrusion process out and develops there macromastia.

Unexpectedly, we found that the addition of block copolymers with the structure of thermoplastic elastomers mixed with polyolefins increase the speed of defect-free extrusion of polyolefins, if the ratio of the elastic modulus to a viscous modulus at a characteristic frequency of occurrence of defects for additives is significantly different from the corresponding value for thermoplastic polymer. Supposedly increase the speed of defect-free extrusion using the proposed additives can occur by two different mechanisms.

First, when using additives, which, when the molding temperature and on the frequency instability of f are characterized by elasticity greater (at least 20%)than the polymer material, i.e. the (G'/G")|Supplement>1,2·(G'/G")|polymerthe deposition of elastic additives creates an elastic coating on the wall. Microcracks that extend along the deformed shear elastic coating, do not deviate from the wall as the floor is a source of elastic energy. The passage of microcracks shift races who love moves along the surface of contact. Sliding speed corresponding to the amount of changes per unit of time (.Gerde, M.Marder, Nature, 413 (2001) 285 [24]). Because of the shear cracks propagated along the surface of contact, the thickness of the elastic coating is not as important as its length, and the coating exhibits elastic properties even at a thickness of about 60 nm.

Secondly, when using additives, which have a low elasticity compared to the polymeric material (at least 20%), i.e. the (G'/G")|Supplement<0,8·(G'/G")|polymer, micro-cracks along the surface of the mouthpiece does not apply. Supplements based on block copolymers with a low elasticity as if glued the melt polymer material to the wall and prevent its detachment near the exit of the mouthpiece.

The frequency instability of the melt is characterized by the ratio of the elastic modulus to a viscous modulus (G'/G")|polymer=K. the Value of K can be taken for option of elasticity on the frequency of occurrence of defects. In the case of extrusion of polyethylene LL1201 XV at a temperature of 165°and used in example 1 steel mouthpiece 6·32 mm K=1,4. Improving the speed of defect-free rate of extrusion is especially great if additives are made one of two conditions: (G'/G")|Supplement<1 or (G'/G")|Supplement>To2.

The additive block copolymers are precipitated in the process of extras is Ziya on the surface and displace polyolefins, as the adhesion block copolymers to the surface is higher than the adhesion of a non-polar polyolefins. Elastic coatings facilitate the propagation of microcracks shift along the coating, and inelastic coatings inhibit their spread. In both cases, eliminates gaps polymer inside the mouthpiece, which appear from the outside as defects "snake" and "shark skin. When using elastic additives propagation of microcracks along the wall of the mouthpiece even easier, if the molecules of such additives is thermodynamically incompatible with polyolefins. Block copolymers based on polyurethanes are characterized by good adhesion to the surface and tensile strength, so their use as additives is preferred. As hard segments selection of aromatic diisocyanates are preferable to the aliphatic diisocyanates. As soft segments is better to choose the siloxanes and fluorinated hydrocarbons. Siloxanes containing two or more silicon atoms linked by one or more oxygen atoms. Commercially available polysiloxane structure polydimethylsiloxane and polymethylphenylsiloxane. Polymethylphenylsiloxane and polydimethylsiloxane are very flexible (soft) molecular chain, as neighboring bonds between atoms of silicon and oxygen may like a pair of scissors to change the angle between them. These polymers are characterized by an extremely low glass transition temperature (-86°and -123°respectively). Morphology and mechanical properties of block copolymers of polydimethylsiloxane with polyurethane and urea disclosed in the technical literature (http://scholar.lib.vt.edu/theses/available/etd-72698-13572/unrestricted/Disswhl2.pd [25]; US Patent No. 3562352, Emery Nyilas, "Polysiloxane-Polyuretane block copolymers", Feb.9, 1971, US Class: 260-824, MKI: C 08 G 41/04 [26]; US Patent No. 6291587, Bleys Gerhard Jozef, et al. Sep.18, 2001, "Elastomers from compositions comprising rigid thermoplastic polyurethane", US. Class: 525/131, MKI: C 08 L 009/00 [27]; 1. US Patent No 6627724, Gordon Francis M, et. al., "Polysiloxane-containing polyuretane elastomeric compositions", Sep.30, 2003, US Class: 528/26, MKI: C 08 G 77/458 [28]).

Fully fluorinated polyethylene known under the trademark Teflon and is also characterized by a low glass transition temperature (-73°). So good results as elastic additives should provide thermoplastic elastomers based on block copolymers of aromatic diisocyanates (polyurethane) with siloxanes or fluorinated polyethylene, characterized at the temperature of molding a higher elasticity in comparison with the polymer matrix.

Inelastic cover better suppress the spread of cracks, if they are thermodynamically compatible with polyolefins. As the hard segments of the polyurethane aliphatic hydrocarbons is thermodynamically more compatible with polyolefins, and as soft behold the cops - polyethers. But, in order to increase the adhesion of the additives to the metal used as soft segments polyesters can be justified. So good results as inelastic additives should provide block copolymers of aliphatic diisocyanates (polyurethane) with simple and complex polyesters characterized at the molding temperature and the characteristic frequency of occurrence of defects less elasticity in comparison with the polymer matrix. In General, polyesters, can be characterized by a melting point above room temperature and, respectively, at room temperature block copolymers diisocyanates (polyurethanes) and such polyesters will not be elastic. In contrast to thermoplastic elastomers, in industry they are used as adhesives (adhesives).

In the technique of extrusion of the additive prepared in the form of concentrated mixtures with a polymeric material, and pellets of the concentrate is metered and mixed with granules of polymeric material in the extruder. Preparation of concentrated mixtures of additives with the share of additives in polymer material 1 to 10 parts per hundred enables you to optimize the size of the inclusions additives in the polymeric material. Concentrated blend of additives with polymers can also be used for extrusion rapid application covered the th on the equipment for molding. Preferably for the preparation of the concentrate to use the same polymers that form the basis of a thermoplastic material, but in General for the preparation of concentrated mixtures can be used a material that is different from the main component. For example, a concentrated blend of additives (1-10 parts per hundred) with low density polyethylene (LDPE), which is not affected by the occurrence of defects during extrusion, can be used for dry dosing of additives in the extrusion of linear low density polyethylene (LLDPE), which is prone to the appearance of defects during extrusion.

The precipitation of the additives on the surface of the forming device is in places a sharp narrow stream. The size of the inclusions cannot be too small (less than 0.1 µm), as in this case, significantly reduced the rate of deposition of additives on the walls of the forming device. The size of the inclusions cannot be too large (>10 μm), as becomes evident heterogeneity of the obtained product. Under the optimal size of the inclusions (from 0.1 to 10 μm) content of additives in thermoplastic material may not be below 10 parts per million or more than 1 part in a hundred. Indeed, the deposition efficiency of additives increases with the size of the inclusions (S.B.Kharchenko, P.M.McGuiggan, K.B.Migler, "Flow induced coating of fluoropolymer additives: development of frustrated total inernal reflection imaging", Journal of Rheology, 47 (2003) 1523-1545 [29]. If the content of the additives is less than 10 parts per million, while the optimal size of inclusions in the melt deposition of additives on the surface is uneven. The content of the additives is more than 1 part per hundred leads to an excessive increase in the thickness of additives on the surface, therefore, concentrates with the content of additives from 1 to 10 parts per hundred can be used for pre-coating additives on the equipment or for dry dosing additives in thermoplastic polymeric material.

The essence of the invention is illustrated graphic materials and examples of implementation. Figure 1 graphically presents for temperature 165°With the change of the elastic modulus G' and viscous modulus G" with frequency of exposure f=ω/2π for linear polyethylene LL1201. Figure 2 presents schematically the device for attaching the mouthpiece. 3 shows the characteristic curve of extrusion obtained with the use of steel mouthpiece, and the measured values of the frequency of occurrence of defects "shark skin".

4 shows a characteristic curve obtained using a glass mouthpiece, and frequency of occurrence of defects "shark skin". Figure 5 presents the characteristic curves obtained with the use of steel mouthpiece and elastic coatings, thermoplas the practical elastomers. Figure 6 presents the curves of change of a ratio of elastic and viscous modulus polyethylene and thermoplastic elastomers based on polyurethane and polysiloxane at a temperature of 165°C. figure 7 presents the characteristic curves obtained with the use of steel mouthpiece and inelastic coatings thermoplastic elastomers. On Fig presents the curves of change of a ratio of elastic and viscous modulus polyethylene and thermoplastic elastomers based on polyurethane and polyesters (165°). The Table presents the values of the critical speed of extrusion, in which there is the formation of defects on the surface of the polyethylene.

Example 1.

The extrusion of polyethylene LL1201 XV production company ExxonMobil (http.V/www.exxonmobil. com/chemical [30] was performed using a mouthpiece without coatings. The device for attaching the mouthpiece is presented schematically in figure 2. The device comprises a bearing body 1 with devices for securing it to the extruder, the mounting pin 2, ring 3, fixed on the bearing housing, an annular plate 4 to install the mouthpiece screws 5 to the fixing ring plate 4 and the casing 3 to the bearing housing 1, the mouthpiece 6 in the form of a tube extrusion rod. On the inner surface of the mouthpiece coating 7, which may be a coating containing metal oxides to lucchinetti elastomers to metal surface or coating of the elastomer. The device includes a pressure sensor 8 and the screw cap 9. The molten polyethylene is shown in gray.

Used polyethylene is characterized by the following parameters: the density is 0.926 g/cm3the melting point is 123°C, the melt index is 0.7 g for 10 minutes, the manufacturer's recommended temperature extrusion - 180-200°C. For extrusion used piston extruder production company Loomis (http://www.loomisproducts.com [31]) with a diameter of camera for material - 60 mm, length 200 mm, with a maximum chamber pressure of 400 ATM. The piston extruder was set in motion by a hydraulic cylinder. The chamber was equipped with heaters to heat up to 210°C, and the temperature of the chamber walls was measured with thermometer - thermocouple. Heating of the mouthpiece provided with an additional motor heater with temperature measurement thermometer - thermocouple. Additionally, the temperature of the released product and the temperature of the tip was measured in a non-contact thermometer - a thermometer. The pressure in the chamber was measured by a sensor with an accuracy of 0.5% in the range from 0 to 100 ATM. The movement of the piston controlled by the computer and measured by the position sensor with a precision of 5 μm. Electrical signals from the position sensor and the pressure sensor is converted into a digital signal with an accuracy of 24 bits and every 0.6 seconds re the awali on the serial ports of the computer. The control parameters and the measurements were made using the software package LabView 6.0 and Pentium 4 computer. Coming out of the mouthpiece 6 product shot digital camera SONY Digital 8 DCR-TRV110E with a frequency of 25 frames per second. The backlight of the product was carried out by the strobe, synchronized with the camera, to avoid blurred image due to the movement of the product. The survey was started simultaneously with the beginning of the extrusion process, therefore, the appearance of defects on the surface of the product can be had with high accuracy to correlate with the speed of the outgoing product.

First used transparent glass mouthpiece. Emerging from the glass mouthpiece product at low speeds has a smooth glossy surface, then observed the occurrence of a periodic surface defects. By increasing the speed of extrusion of the scale defects were increased in length, and the height of the relief. With increasing speed of 100 mm/sec plots defective surface followed by areas of smooth surface and the product resembled the trunk of bamboo. When observed between crossed polarizers at the time of the appearance of surface defects near the output tip of the glass tube was observed by the appearance of bright spots of 0.5 mm in length along the flow axis, which showed the appearance of preferential orientation of the molecules of the polymer. Critical LINEST is I the speed of the appearance of surface defects at a temperature of 165° With $ 5.6 mm/sec. The appearance of preferential orientation of the polymer indicates the stretching of the material near the exit of the mouthpiece.

Then we made the extrusion of molten polyethylene at a temperature of 165°through the cylindrical mouthpiece 6·32 mm stainless steel. Before the experiment, the tip was heated in an open flame to a temperature of about 600°to burn all organic contamination that could be present on the wall, and to obtain a layer of oxide on its surface. During the first 30 minutes we were in the extrusion at an average speed of about 1 mm/sec to reach equilibrium thermal and mechanical state of the device, and then spent the extrusion with the speed increase from 1 to 400 mm/sec. The obtained characteristic curve presented in figure 3 as a solid line. At low speed extruded product had a smooth surface, then at a speed of about 4.5 mm/sec began to scatter light, and at speeds of more than 5.4 mm/sec of a typical defects such as "shark skin". When defects are marked on the curve cross. With the increase in the rate of extrusion as the period and depth of the defects was increased similar to the case of extrusion through a glass mouthpiece. The temporal frequency of the surface relief on the product in [Hz], i.e. the ratio of the extruding speed in [mm/s is to] to the period of the surface relief in [mm] were measured and represented in figure 3 by the dotted line. Oscillations in the pressure and large-scale distortion of the surface we observed at speeds above 100 mm/sec. The temporal frequency of occurrence of defects on the surface at low speeds and at speeds above 100 mm/sec - near. This observation testifies in favor of the explanation that the surface defects appear due to the periodic transitions of the thread from sticking to the slide near the exit of the mouthpiece. As can be seen from the graph, the frequency of occurrence of defects varies little with increasing the linear speed of extrusion. Observed for steel mouthpiece 6·32 mm frequency of occurrence of defects lies near the mean value of the frequency 19-20 Hz. The ratio (G'/G")|polymerthe elastic modulus to the viscous module for molten polyethylene at a frequency of 20 Hz is about 1.4. For comparison in figure 4 shows the characteristic curve, and the frequency of occurrence of defects "shark skin", obtained using the tip of a glass tube, 3,3·24 mm can be Seen that with the change of the material and the geometry of the mouthpiece characteristic frequency of occurrence of defects does not change much (from 20 to 26 Hz).

Example 2.

After the experiment the extruder was purged of residual polyethylene, and the mouthpiece is removed and annealed in an open flame, as described above. After cooling to a temperature of less than 200°With a mouthpiece filled with material additives to increase defect-free rate of extrusion to their melting and filling the polymer volume of the mouthpiece. The mouthpiece in the process of completing fueled. The extruder was filled with polyethylene and stood before the establishment of thermal equilibrium at least 8 hours. Then the mouthpiece secured to the extruder and perform slow extrusion for 30 min in order to squeeze the elastomer from the mouthpiece, smooth and reduce the thickness of its layer on the surface. The characteristic curves obtained with the use of fluorinated polymer Viton® FreeFlowTM SC-PW", elastomers TPSE-160, TPSE-120, TPSE-80 from Wacker Chemie, shown in figure 5. The time of occurrence of defects on the surface of the product is shown a cross on each curve. The thickness of the coating after the extrusion was evaluated by measuring the electrical capacitance between the steel mouthpiece and saturated conductive solution of sodium nitrate. Figure 6 graphically presents for temperature 165°With the change of the elastic modulus G' and viscous modulus G" with frequency of exposure f=ω/2π for linear polyethylene LL1201, elastomers TPSE-160, TPSE-120, TPSE-80 and fluorinated polymer Viton® FreeFlowTM SC-PW". Table 1 shows the results of measurements of the critical rate of occurrence of defects on the surface of the product and the relationship of the elastic and viscous modulus at a frequency of 20 Hz. You can see a General trend that increasing the velocity defect-free extrusion is that the more elastic compared to the melt of polyethylene I have is a thermoplastic elastomer on the frequency, close to 20 Hz.

Example 3.

In the same way as described above, the mouthpiece filled elastomers "D12C75", "D15N70", from Mentquisa, "Baymod PU-A" from Bayer and perform the extrusion. The characteristic curves shown in Fig.7. Reducing the pressure of the molding, i.e., the slip of molten polyethylene along the surface of the mouthpiece, at low extrusion speeds within the accuracy of the changes have been recorded. The time of occurrence of defects on the surface of the product is shown a cross on each curve. On Fig graphically presents for temperature 165°With the change of the elastic modulus G' and viscous modulus G" with frequency of exposure f=ω/2π for linear polyethylene LL1201 and elastomers elastomers "D12C75", "D15N70" and "Baymod PU-A". The moment of sudden changes in pressure, i.e. the transition to the slide, shown in curves a straight vertical line. It is seen that a sharp decrease in pressure which is caused by disruption of the flow in macroscopic sliding along the surface of the mouthpiece is the later, the more speed defect-free extrusion can be obtained by using additives. This further shows that the use of the proposed inelastic additives "glues" the melt of the polymer to the wall of the mouthpiece. Table 1 shows the results of measurements of the thickness of the coating elastomers after extrusion, the dynamic viscosity at a frequency of 20 Hz, the critical is Kai the rate of occurrence of defects on the surface of the product, the ratio of elastic and viscous modulus at a frequency of 20 Hz. It is seen that the increase in the rate of defect-free extrusion is greater, the less elastic compared to the molten polyethylene is a thermoplastic elastomer with a frequency close to 20 Hz.

Table 1
FloorThe coating thickness, micronsCritical velocity, m/sG'/G" @ 20 Hz
Without coating-of 5.4K=1,4
VITON0,07130,7·2=To
TPSE-800,45981,22·2
TPSE-1600,091421,22·2
TPSE-1200,641031,38·2
TPSE-1400,361361,53·2
D15N70No data180,81·K=1,14
D12C750,08470,71·K=1
Baymod PU-ANo data680,51·K=0,72

Example 4.

In the same way as described above, the mouthpiece was purified and the chamber of the extruder was filled with a mixture of elastomer "TPSE-160" from Wacker Chemie with polyethylene and perform the extrusion. The mixture was prepared as follows. A thermoplastic elastomer was dissolved in hot isopropanol at a concentration of about 5% and the resulting solution was poured into the package 1 kg of pellets of polyethylene. Then the compressed air granules were mixed and dried from isopropanol. Thermoplastic elastomer covered the surface of the granules and layout of the frozen drops of irregular shape with dimensions of 1 to 100 μm. These granules were loaded extruder, as described above. We spent the extrusion speed of about 50 mm/sec and watched in the extrusion process defects. First, on the surface appeared strips, free from defects, and in the extrusion process area, free from defects, grew up to complete disappearance of defects on the surface. With a share of additives about 100 parts per million needed to carry out the extrusion of about 10 meters product to get rid of defects. With a share of additives 200 ppm - 4 m With a share of 2000 parts per million defects disappeared after extrusion 0.5 m of the product.

The induction time or the length of the product that you want to squeeze until the disappearance of defects depends on the content of additives almost linearly, and to accelerate you to extrusion with a high content of additives, and then the content of additives to reduce. The content of additives to 100 parts per million, at which we observed without effektnuiu extrusion, about 4 times less than the content of additives fluorinated polymers used commercially at the present time. The findings also show that a specific effect of additives can be recorded even when the proportion of additives 10 parts per million.

Therefore, the proposed technical solution to increase defect-free speed extrusion of polyolefins propose to use the block copolymers, which are commercially available at present for the manufacture of shoes and to increase the impact strength of brittle polymers. The proposed additions, primarily on the basis of polyurethane, can be a cheap substitute currently used additives based on fluorinated polymers. Professionals should be clear that the proposed solution may not be limited to polyolefins, but can be effectively used in the extrusion of films and fibers made of other polymers, proteins and viscose, which are prone to the appearance of defects in the molding. Layer additives, which is deposited on the metal surface, not only increases the speed of defect-free extrusion, but also allows to reduce the corrosion of metal mouthpiece or dies due to decomposition of the polymeric material or the contact of the metal with liquids in coagulating baths.

It should be noted that in the prior art do not track is no obvious way the use of block copolymers containing hard and soft segments and having certain mechanical properties, increases the speed of defect-free extrusion of polymer melts. The effect of suppression of defects during extrusion of polyethylene with the addition of block copolymers was not previously known from the patent and technical literature. Thus, the proposed solution meets the requirement of inventive step.

So, the proposed solution is a new, meets the criterion of "inventive step and is industrially applicable and, therefore, is characterized by all the necessary features of the invention.

1. Thermoplastic polymeric material comprising as the main component of the polyolefin in an amount of from 0.001 to 10 parts by weight per 100 parts by weight of thermoplastic polymer material additive to improve processing by extrusion material, wherein the additive is a block-copolymer-based diisocyanates with a softening temperature below the molding temperature of thermoplastic.

2. The material according to claim 1, characterized in that the additive is present in an amount of from 0.01 to 1 parts by weight per 100 parts by weight of thermoplastic polymer material.

3. The material according to claim 1 or 2, characterized in that the block copolymer on the basis of diisocyanates represents the POC-copolymer, based on aromatic diisocyanates.

4. The material according to claim 3, characterized in that the block copolymer on the basis of diisocyanates is a block copolymer of polyurethane with simple or complex polyester.



 

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