JPH0344892B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a method for improving the fluid permeation resistance of heterogeneous laminate blends of polyolefins and polyolefin-incompatible condensation polymers. As described in detail in U.S. Pat. Stretch the melt,
BACKGROUND OF THE INVENTION Processes for producing laminates of polymeric materials, and products made therefrom, comprising the step of forming a melt blend by cooling the stretched material below the melting point of the lowest melting polymeric component, are known. The fluid permeation resistance of the product thus produced is superior to that of conventional heterogeneous blends of similar ingredients. The present invention relates to a method of improving the fluid-repellent properties of a molded article as described in US Pat. No. 2,410,051 by stretching the article to 2 to 6 times its original dimensions. More particularly, the invention comprises a substrate polyolefin, a condensation polymer incompatible with the substrate polyolefin, and an alkylcarboxyl-substituted polyolefin, the substrate polyolefin having a melting point lower than the melting point of the condensation polymer. , and is present in the molded article in the form of a continuous matrix phase, and the condensation polymer is present in the molded article as thin, substantially two-dimensional, parallel, overlapping layers in a discontinuous, dispersed form. , an alkylcarboxyl-substituted polyolefin is present between the matrix and the layer and adheres the matrix and the layer to each other. Stretching the molded article to 2 to 6 times its original size at a temperature higher than a temperature at which a significant portion of the substrate polyolefin crystals becomes molten and lower than a temperature at which all the crystals melt. A method is provided. The products stretched in the method of the present invention are described in detail in the above-mentioned US patent application Ser. No. 241,051. Generally, these products are laminate molded articles made from a mixture of two incompatible polymers and one polymer that is used to bond the laminated regions of the incompatible polymers together. It is. This molded product is
By mixing the polymer particles together, heating the mixture to create a heterogeneous melt of the material, and shaping the melt by stretching the melt into an elongated, discontinuous polymer phase. able to make. In one embodiment of U.S. patent application Ser. After that, be careful to avoid further mixing. In other embodiments, the polymer particles can be combined in a softened or molten state so long as the polymer particles retain non-uniform properties when combined. The formulation also includes mixing the polymers at a temperature at which the polyolefin or condensation polymer softens or melts;
This can then be produced by heating it. The production of this article relies on the production of incompatible molten heterogeneous blends, in which the melt is heated at a temperature above the melting point of the highest melting polymer component.
For example, when stretched by an extrusion force, one polymer creates a continuous matrix phase and the other polymer creates a discontinuously distributed phase. The polymers forming the discontinuous phase are present in multiple thin, substantially two-dimensional, parallel, overlapping layers that are embedded within the continuous phase. To make the molded articles of US Patent Application No. 241,051, a polymer is required that adheres adjacent layers or regions of incompatible polymers. From the standpoint of this purpose, this polymer can be described as a compatibilizer, although the exact mechanism of its function is not completely understood. In the laminate molded product of the present invention,
Between each adjacent layer of incompatible polymers, at least some compatibilizer is concentrated and partially binds one layer to the other, bonding the two layers together. It is believed that Without compatibilizers, the mechanical properties of molded articles made from heterogeneous melts of incompatible polymers will be poor.
As used herein, the term "incompatible polymers" refers to materials that are substantially immiscible with each other in the molten state. Although not required, it is preferred that the condensation polymer used be in particulate form, and it is desirable that both the polyolefin and the condensation polymer can be mixed in particulate form. Generally, the size of this particle is determined when the melt blend of incompatible polymers is placed into a suitable melt-stretching device, such as the lip of an extrusion die, or an injection mold.
The particle size must be such that it has the necessary non-uniformity to produce the articles of No. 241051. If the particles, especially those of condensation polymers, are too small,
The melt blend acts as a homogeneous composition because the areas of material that are not well mixed and yet create a discontinuous polymer phase are very small. If the particles, especially those of condensation polymers, are too large, the melt blend will tend to create a marbleized rather than a layered structure, with large areas of material creating discrete phases forming This causes the material that extends to the opposite boundary of the product and makes up the continuous phase to be severed. It is preferred that these particles are generally regular in shape, for example cubic or spherical. However, it is also possible to have an irregular shape and, if appropriate, to use shapes with one dimension larger than the other, for example flakes or fibers. When the respective incompatible polymers are present as individual particles, the particles are generally about the same size, although this is not necessary. The compatibilizer itself can be supplied in particulate form or can be mixed, coated or otherwise combined with all or part of one or both of the incompatible polymers. can. In the molded articles of US Patent Application No. 241,051, the thickness of the layer of discrete phase material is a function of the particle size and the degree of elongation of the molding process. Generally, the particle size of the polymer that becomes the discontinuous phase is approximately 0.5 to 50μ thick after stretching the melt.
m or slightly thicker to produce superimposed layers. As explained in detail below, when stretched by the method of the present invention, the thickness of this layer is reduced to about 0.05-10.0 microns. Mixing of the polymers can be carried out in known manner, for example by V-blenders or shaker mixers or, on a large scale, by double cone mixers. Continuous mixing of particles can be accomplished in several known ways. Of course, the particles can also be mixed by hand; the only requirement for mixing is that two randomly taken samples of a given material have substantially the same composition. It is a must. Mixing of incompatible polymers is accomplished by adding the higher melting point polymer to the melt of the lower melting point polymer, which is kept below the melting point of the higher melting point polymer. In this case, the melt is stirred to form a suitable mixture. This mixture can be used as is for the heating process. Once mixed, each incompatible polymer is heated to a temperature above the melting point of the highest melting point polymer component.
Heating is performed to stretch the softened or molten compound. For the purposes of this specification, for incompatible polymers that do not exhibit a uniform melting point, the melting point is defined as the softening of the polymers to the extent necessary to stretch each polymer in the formulation. means at least sufficient temperature to This heating results in a softening of the material or a molten, non-uniform blend. This heating must be done in a manner that avoids further mixing of incompatible polymers. This is because such mixing causes the melt particles to homogenize and coalesce, resulting in a melt or molded article with a uniform, non-lamellar composition. This heating can be done in several known ways, usually in an extruder. The use of a single-screw extruder, such as a type of extruder designed to transport materials rather than mixing them, during the heating and forming steps can reduce the homogeneity of two-phase, incompatible polymer compositions. No change will occur. Low-shear, low-mixing extruders of the type commonly used for polyvinyl chloride, acrylonitrile, or polyvinylidene chloride, if used in a manner that melts and transports the material and minimizes mixing of the components;
can be used. High shear, high mixing extruders of the type commonly used for nylon and polyethylene are generally not available. To produce the molded article of U.S. Patent Application No. 241,051, the melt is stretched and cooled; this stretching stretches the two-phase melt and substantially changes the size of the particles of the discrete phase. It is. Stretching in the molten phase can be carried out in several ways or in combinations of these methods. For example, the melt can be stretched between rollers, pressed between platens, or extruded between the lips of a die. Molding methods such as blow molding can also carry out the expansion of the present invention. When manufacturing containers as molded articles, this stretching involves extruding a heterogeneous melt formulation to create a container preform, or parison, and then blow molding the molten parison to form the finished container. This can be achieved by combining the steps of The stretching of US Patent Application No. 241,051 can be carried out in one direction, ie, in the vertical direction, at a temperature above the melting point of the highest melting polymer component. Whether stretching is carried out in one direction or in two directions, it must be carried out in at least one direction by 100-500%, preferably 100-300%. The upper limits described herein are not critical unless the molded article ruptures, but the lower limits are important unless improper stretching results in the fluid permeation resistance characteristic of U.S. Patent Application No. 241,051 not being improved. After stretching, the molded article is solidified by cooling to a temperature below the melting point of the lowest melting point component. Cooling can be done in any desired manner and at any convenient rate.
When molding is performed by blow molding, the mold is often cooled to cool the molded product. When extruding the film, cooling can be performed by applying chilled air or by contacting it with a quench roll. Regarding the proportions of the components of the product of US Patent Application No. 241,051, the incompatible polymers to become the discontinuous phase of the molded article should generally be present at no more than about 40% by weight of the mixture. More specifically, the incompatible condensation polymers should be present in an amount of at least about 5% and no more than about 40% by weight of the mixture, with about 10-30% being preferred. If the polyester is an incompatible polymer, the incompatible polymer can be present up to about 60% by weight of the mixture. The polyolefin should be present in an amount of at least about 60% and no more than about 95% by weight of the mixture, with 70-90% being preferred. The compatibilizer should be present at about 5-30% by weight of the discontinuous phase, with about 10-20% being preferred. Inert fillers can be incorporated into any of the ingredients, so long as the fillers are not of such type or amount as to interfere with the formation of the layered structure or the desired or necessary properties of the composition. Amounts of matting agents, colorants, lubricants, stabilizers, etc. commonly used in structural polymers can be used in the present invention. The amount of such filler is not included in the calculation of the amount of incompatible polymer and compatibilizer. The polyolefins used in the composition of the molded article of U.S. Patent Application No. 241051 include polyethylene,
Includes polypropylene, polybutylene, copolymers of these materials, and the like. Polyethylene is preferred and can be high density, medium density, or low density polyethylene. Condensation polymers that are incompatible with polyolefins are polyamides, polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polycarbonates. Preferably, the polyolefin and condensation polymer are selected such that the melting point of the polyolefin is lower than the melting point of the condensation polymer. Polyamides and polyamide copolymers are known and are made by reacting carboxylic acids with primary amines under known conditions. Examples of carboxylic acids used in the production of polyamides include:
These include adipic acid, suberic acid, sebacic acid, azelaic acid, glutaric acid, and pimelic acid. Examples of polyamides include tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, octamethylene diamine, and the like. Examples of polyamides include poly(pentamethylene adipamide), poly(hexamethylene adipamide), poly(hexamethylene sebaamide), lactams such as caprolactam and amino acids such as 11-aminoundecanonic acid. This includes polyamide, etc. Poly(hexamethylene adipamide) and polycaproamide are preferred. Polyesters are known and are made by reacting dibasic carboxylic acids with glycols under known conditions. Examples of carboxylic acids used in the production of polyesters include terephthalic acid, isophthalic acid, and the like. Examples of glycols are ethylene glycol, butylene glycol and the so-called polymethylene glycols having from 2 to 10 methylene groups. Examples of polyesters are poly(ethylene terephthalate), poly(butylene terephthalate), and the like. Poly(ethylene terephthalate) is preferred. Polycarbonate was manufactured by C.R.C., Cleveland, Ohio, USA.
Published in 1971 by CRC Press, edited by WJ Roff and JR Scott, Handbook of Common Polymers. Alkyl carboxy-substituted polyolefin compatibilizers are polyolefins in which the carboxyl moiety is attached to the polyolefin back bone itself or to a side chain. The term "carboxyl moiety" means a carboxyl group selected from the group consisting of acids, esters, anhydrides, and salts. A salt of a carboxylic acid is a neutralized carboxylic acid, and a compatibilizer containing a carboxylic acid as a carboxyl moiety is meant to contain the carboxylic acid of this salt. Such compatibilizers are called ionomeric polymers. Compatibilizers can be synthesized directly or made by graft polymerization. An example of a direct synthesis method is a method in which an α-olefin is polymerized with an olefin having a carboxyl moiety. An example of a grafting method is a method in which a monomer having a carboxyl moiety is added to a polyolefin backbone. In the case of a compatibilizer made by a grafting method, the polyolefin is polyethylene or a copolymer of ethylene and at least one α-olefin having 3 to 8 carbon atoms, such as propylene, or at least one α-olefin having 3 to 8 carbon atoms. It is a copolymer of α-olefin and diolefin, such as 1,4-hexadiene. Polyolefins are reacted with unsaturated carboxylic acid, anhydride, or ester monomers to form graft polymers. Representative suitable unsaturated carboxylic acids, anhydrides, or esters include: methacrylic acid, acrylic acid,
Ethacrylic acid, glycidyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, diethyl maleate, monoethyl maleate, di-n-butyl maleate, maleic anhydride, maleic acid, fumaric acid, itaconic acid , monoesters of such dicarboxylic acids, dodecenylsuccinic anhydride, 5-norbornene-
2,3-anhydride, nadic anhydride (3,6-endomethylene-1,2,3,6-tetrahydrophthalic anhydride), and the like. In general, graft polymers are approximately 0.01
% to about 20, preferably from about 0.1 to about 10, most preferably from about 0.2 to about 5% by weight of graft monomer. Graft polymers are described in detail in US Pat. No. 4,026,967 and US Pat. No. 3,953,655. In compatibilizers made by direct synthesis, the polymeric materials are α-olefins with 2-10 carbon atoms and α,β with 1 or 2 carboxyl moieties.
- copolymers with unsaturated carboxylic acids, anhydrides, or salts. Compatibilizers made by direct synthesis contain at least 75 mole percent olefinic component and about 0.2
It is made from ~25 mol% carboxyl component. Ionomeric compatibilizers are preferably made from directly synthesized compatibilizers and are composed of about 90-99 mole percent olefins and about 1-10 mole percent α,β-monomers with carboxyl moieties. It is preferable that the At this time, the carboxyl moiety is considered to be an acid equivalent, and when the carboxylic acid equivalent is a monocarboxylic acid, it is neutralized with a monovalent to trivalent metal ion, and when the carboxylic acid equivalent is a dicarboxylic acid, it is neutralized with a monovalent metal ion. Neutralized with valent metal ions. To control the degree of neutralization, the metal ion should be at least 10
% of the carboxyl moieties. Representative suitable α-olefin and unsaturated carboxylic acid, anhydride, and ester monomers are as described above. Ionomeric polymers are described in detail in US Pat. No. 3,264,272. Compatibilizers generally contain about 0.5-3.0% by weight carboxyl component. When making the molded article of U.S. Patent Application No. 241051,
Generally, polyolefins are used to create a continuous phase,
This is used in an amount of about 60 to 95% by weight of the total composition, while creating a discontinuous phase with an incompatible polymer, which is used in an amount of about 5 to about 40% by weight of the total composition. be done. The alkylcarboxy-substituted polyolefin is used in an amount of about 0.5 to 5% by weight, but larger amounts can be used if desired. In accordance with the present invention, the product of U.S. patent application Ser. At temperatures above but below that which melts all the crystals, about 2 to 6 of its original size.
Stretch uniaxially or multiaxially. In this temperature range, the polymer matrix can be stretched without adversely affecting its morphology. This temperature range is expressed relative to a conventional differential thermal spectrometry (DSC) melt curve (heating rate 10°C/min) for the particular substrate polyolefin used. For example, the starting point of this curve for typical high density polyethylene is about 98°C and the ending point is about 135°C. Using this curve, the appreciable portion of the high-density polyethylene crystal is approximately
It can be seen that it melts at 115°C, but all the crystals finish melting at the end point of this curve, ie at about 135°C. Therefore, when the molded article of U.S. Patent Application No. 241,051 is stretched to 2 to 6 times its original size, if the substrate polyolefin is high density polyethylene,
The temperature of the molded article should be approximately 115-135°C. If an attempt is made to stretch this molded article below this temperature, the molded article will fracture. As an example of the method of the present invention, U.S. Patent Application No. 241,051
The molded article in the form of a film made in No. 1 can be stretched in the transverse direction with a tenter frame device and in the machine direction with conventional stretching rolls. The injection molded article in the form of a cylindrical preform of US Pat. No. 2,410,051 can also be multiaxially expanded into a bottle-like container by reheat blow molding. Surprisingly, although the condensation polymer within the substrate polyolefin is stretched during the process of the present invention, as evidenced using optical microscopy with crossed polarizers,
The integrity of the stretched part is retained. That is,
No voids were observed even after stretching. It is inferred that the ability of the condensation polymer within the substrate polyolefin matrix to stretch at temperatures well below the melting point of the condensation polymer is the result of structural interactions between the molecules of the polymer components. Regardless of the mechanism, the product of the process of the present invention exhibits improved fluid permeation prevention properties by a factor of about two to several times per unit thickness compared to the product described in US Pat. No. 2,410,051. The invention is illustrated in detail by the following examples. Example 1 A polyolefin, a polyamide, and a compatibilizer were mixed as follows to make a heterogeneous blend as described in US Patent Application No. 241,051. The polyamide was made by condensing hexamethylene diamine, adipic acid, and caprolactam to obtain a composition of 77.5 parts by weight poly(hexamethylene adipamide) and 22.5 parts by weight polycaproamide. The DSC melting point of polyamide is approximately 225°C. Polyolefin has a density of 0.944g/cc, ASTM
Melt coefficient 0.24g/10 determined by D-1238 method
It is a linear polyethylene with a DSC melting point of approximately 135°C and is manufactured by EI du Pont de Nemours & Company under the trade name ``Alathon PE 7810.''
and Company). The polyamide and polyethylene particles were generally cubic, approximately 3-4 mm on each side. The alkyl carboxyl substituted polyolefin compatibilizer was obtained by melt grafting fumaric acid onto polyethylene having a density of 0.958 g/cc and a melt coefficient of approximately 10 g/10 seconds as determined by the ASTM D-1238 method. Fumaric acid was grafted to polyethylene in an amount of about 0.9% by weight, based on the total weight of the polymer, by the method described in US Pat. No. 4,026,967. Compatibilizers are generally cubic particles with side lengths of approximately 2 to
It was 3mm. The DSC melting point of this material was approximately 135°C. This mixture contains 82% by weight polyolefin, 15% by weight polyamide, and 3% by weight compatibilizer. This was shaken in a drum to ensure a completely even distribution of particles. A portion of this mixture is transferred to an extruder, such as a Midland Ross extruder of New Brunswick, New Jersey, with a low mixing screw and a side-fed blown film die. It was supplied directly to the mold. A film sample with a circumference of about 30 cm was blow molded using a 2.5 inch die at an extrusion temperature of 280°C. For control purposes, the fluid permeation resistance of this film, which was not stretched by the method of the present invention, was measured as follows. 12.7 cm (5 inch) square control film sample 1
and 2 at 225°C and 10.3 MPa (1500 psig) using a hydraulic press equipped with a 4-inch ram such as Model P-204 manufactured by Pasadena Hydraulics, Pasadena, California, USA. It was pressed for 5 minutes to smooth it. For these control samples, we used glass bottles with open metal stoppers, such as those used for bottling food products, recorded the initial weight of the test bottles and film, added toluene, and conducted the test for about 10 days. Permeability to toluene was tested by measuring the weight loss of toluene approximately every two days during the period. These film samples used were circular, with an area of 36.4 square cm (5.64 parallel inches)
It was hot. When making these samples for transmission testing, the film is placed over the bottle neck using an O-ring cut from 1.6 mm (1/16 inch) thick neoprene rubber (approximately the same size as the bottle neck). Put it on top,
Seal the jar to prevent leaks. The results of the permeation tests for these control samples are shown in the table below. A square unpressed film sample with an area of approximately 25.8 square cm and a side length of 5.1 cm was doubled by a factor of 3.5 x 3.5 using a film stretching machine at approximately 125°C so that stretching occurred simultaneously in the machine and transverse directions. Stretched axially. Film samples 1, 2, and 3 were tested for toluene permeability in the same manner as the control film. All tests were conducted at room temperature, 22°C. The resulting weight loss and normalized toluene permeation rate (NTPR) were calculated for all samples.
NTPR was determined using the following formula. NTPR = weight loss (g/24 hours) / 5.64 square inches × film thickness (mils) × 1000 However, 5.64 square inches is the surface area of the film exposed to toluene, and the factor of 1000 normally measures the amount of toluene loss. The standard is 1000 square inches.

[Table] Example 2 The composition used in this Example 2 contains 82% by weight linear polyethylene, 3% by weight compatibilizer, and 15% by weight "Nylon" 6/66 (22.5/77.5% by weight). ), and all details are the same as in Example 1. From this composition, a 14 oz. Injection molding was performed using an injection molding machine manufactured by HPM (Gilead, Ohio, USA). The overall height of this preform is approximately 13.7
cm, the outer diameter was approximately 2.4 cm, and the wall thickness was approximately 0.4 cm. According to US patent application Ser. No. 241,051, low shear mixing conditions are achieved when a conventional screw is used at low speed. Injection molding was carried out at a melt temperature of approximately 250°C. The mold was kept at a temperature of approximately 21°C. The injection time was 12 seconds and the cooling time was 9 seconds. Injection and packing pressure was 12×10 ⁷ Pa (17000 psi). Microscopic examination of the cross-section reveals that the nylon exists in layers due to the elongation of the melt as it flows through the gate and cavity of the mold. This preform was screwed into a receiver on a movable table. A piston-actuated center rod moves into the preform and contacts the edges of the preform, preventing it from sagging during the reheating process. The center rod is also
It also serves to introduce gas into the interior of the preform during the expansion process. The elongated feature of the center rod also helps provide some axial orientation. After screwing, the preform is moved to the heating position. At this position, the preform is heated to the desired temperature using a reciprocating electric heater. The holder to which the preform is mounted can be rotated whenever it is in front of the electric heater. Approximately 7 seconds are required to heat the preform. Immediately after the heating process is completed, the preform is
Move to position between the platens of a mold designed to make approximately 950 c.c. bottles. The surface temperature of the preform is measured using an infrared thermometer (Model CH34LC manufactured by Ircon, Niles, Illinois, USA). The average temperature of the preform is probably somewhat lower than the surface temperature mentioned above. The residence time was approximately 20-90 seconds to equilibrate the temperature of the preform. After this residence time, the mold is closed and at the same time an axial force and gas (N ₂ ) pressure are applied to the preform to stretch it. Surface temperature approx.
128-133℃, blowing time about 8 seconds, blowing pressure about 7
Blow at ×10 ⁵ to ×10 ⁶ Pa (100 to 150 psig),
I made a bottle. After the stretch/blow cycle, open the mold and cool the bottle. As a result, the bottle was stretched by 3.4 and 2.0 times in its circumferential and axial directions, respectively.
The average thickness of the bottle walls was approximately 0.2 mm (7.5 mils). For permeation prevention, add 200cc.
Determined by periodic measurements. The permeability was approximately 0.7 g/day. Control Example A pellet formulation with the same composition as in Example 1 was made, but the polyolefin used had a density of 0.963 g/
cc, melting coefficient 0.3 determined by ASTM D-1238
g/10 min linear polyethylene, commercially available from Phillips Chemical Company under the tradename MARLEX EHM6003. This formulation was then molded using an extrusion blow molding machine (Rocheleau Die & Machine, Fitchburg, Mass., USA).
Die & Machine). Bottles of approximately 1 mm size were made by low shear mixing (2:1 screwdriver compression ratio). The die-shaped head is approx.
The temperature was kept at 245℃. Using the above conditions, the product of US patent application Ser. No. 241,051 was made in the form of a bottle. Bottles with different wall thicknesses were prepared using machine parameters and their permeability to xylene was determined. The permeability of an unstretched bottle with wall thickness comparable to Example 2 was calculated to be approximately 3.9 g/day.

Claims (1)

[Scope of Claims] 1 Consisting of a substrate polyolefin, a condensation polymer incompatible with the substrate polyolefin, and an alkyl carboxyl-substituted polyolefin, the substrate polyolefin has a melting point lower than the melting point of the condensation polymer, and present in the molded article in the form of a continuous matrix phase, and the condensation polymer is present in the molded article as thin, substantially two-dimensional, parallel, overlapping layers in a discontinuous, dispersed form;
An alkylcarboxyl-substituted polyolefin is present between the matrix and the layer and adheres the matrix and the layer to each other in a method for improving the fluid permeation resistance of a layered article. The molded article is stretched to 2 to 6 times its original size at a temperature higher than the temperature at which a significant portion of the polyolefin crystals becomes molten, but lower than the temperature at which all the crystals melt. Method. 2. The method according to claim 1, in which stretching is performed in a uniaxial direction. 3. The method according to claim 1, wherein stretching is performed in multiple axial directions. 4. The method of claim 1, wherein the substrate polyolefin is selected from the group consisting of polyethylene, polypropylene, polybutylene, and copolymers of these materials. 5. The method according to claim 1, wherein the condensation polymer is a polyamide. 6. A method according to claim 5, wherein the polyamide is present in an amount of 10 to 20% by weight of the composition. 7. The method according to claim 1, wherein the condensation polymer is a polyester. 8. The method according to claim 1, wherein the alkylcarboxyl-substituted polyolefin is selected from the group consisting of polyolefins in which the carboxyl moiety is bonded to the polyolefin skeleton itself or to a side chain.