RU2213658C2 - Casting - Google Patents

Abstract

FIELD: method for casting of thin-walled tube-shaped container. SUBSTANCE: the method of manufacture of flexible thin-walled articles consists in the fact that polymeric mixture is fused and injected in a mould, then polymer is selected that is resistant to cracking under the action of the stress of the environment exceeding 10 hours, determined by the test results in compliance with the following procedure: (a) casting of a great number of strips of polymeric mixture is accomplished, including any treatment after casting designed for production of a finished article, having cross-section dimensions making up 0.65 mm in thickness and 10 mm in width in the conditions of duration of long flow with a large shift similar to those that are designed for use in manufacture of a flexible thin-walled article; (b) bending of the strips to yourself is conducted and broached by brackets at a distance of 3 mm from the bend; (c) the bent strips are immersed in a solution of an agent causing cracking under the action of stress, for example, in a 10-% solution of matter Terik No.9 and sustained at a temperature of 50C; (d) the strips are examined for the signs of cracking, considering any signs of cracking as a defect; (e) the time to failure is determined as the moment when 50% of the strips manifest the signs of cracking, then polymeric mixture is injected in a mould having a cavity, which produces a thin-walled article, having a thin section, 1 mm thick or less, this thin section is in essence continuous for the space of more than 50 mm in the direction of flow of fused polymeric mixture in the mould. Then the thin-walled article molded of polymeric mixture is extracted from the mould. The thin-walled tube is manufactured by this method. EFFECT: provided casting of articles with long thin sections for their industrial or domestic use, it is guaranteed that polymer will flow well in a long, narrow and curvilinear trajectory and have good mechanical properties. 17 cl, 18 dwg, 14 ex, 3 tbl

Description

 The invention relates to a method of injection molding, in particular to a method of injection molding of products having thin sections, such as thin-walled tube-like containers used in the cosmetic industry for lotions, moisturizers, etc.

 Thin-walled tubular containers, such as those used in the cosmetic industry, are currently manufactured using a combination of extrusion, injection molding and welding methods (referred to herein under the general name "extrusion method"). The tube body is extruded in the form of a continuous cylinder, which is then cut to obtain the required length for the formation of the container body. When implementing a separate injection molding method, a “head and shoulders” of the tube are made. The "head and shoulders" obtained by injection molding are then welded to the extruded tube to form a container. Immediately after filling the container with the product, the rear end of the container is welded, performing an additional welding method. This method of manufacturing tubes has several limitations, the main of which are the high cost of equipment, the inability to obtain a wide range of tube shapes using this equipment, the inability to provide various finishes or embossing of the finished textured surface as an integral part of the manufacturing method, as well as the inability to introduce such accessories and / or elements, like corks and hooks, during the implementation of the manufacturing method. Polyethylene with a low melt flow index (MFI) (MFI is usually less than 2) is the preferred polymer for the manufacture of tubes, because it typically introduces the good feel and flexibility properties required by consumers and suitable for extrusion processing. In addition, low engineering polyethylene provides sufficient product durability and barrier properties to make it suitable for most products currently packaged in tubes. In cases where the barrier properties of polyethylene are not adequate for specific applications, multilayer films of medium density polyethylene (MESP), high density polyethylene (HDPE) and polypropylene (PP) are usually used.

 Although injection molding of products such as thin-walled containers has been proposed for a long time, until now it has not been possible to injection molding such products having relatively long thin sections without making these products too susceptible to damage to be suitable for industrial or domestic use. The main problems associated with the polymers used for injection molded tubes are that the method of forming a tube of cylindrical or other shape requires that the polymer simultaneously have high MFI to ensure that the polymer will flow along a long, narrow and curved path caused by the shape of the tube, without the use of excessive specific injection pressures, and also have good enough mechanical properties to withstand manipulation and be resistant to cracking effects under the stresses of many products that will be packaged in it. In the case of injection molding of a tube, conventional methods will have a requirement that the polymer must have flow properties that allow the formation of molded parts with radiuses of curvature and a length to thickness ratio of 100, and often more. The injection of a “standard” polymer into a mold with such dimensions introduces large stresses into the polymer, and these stresses are transferred to the product, made in such a way that the polymer is rapidly cooled below its crystallization temperature before these stresses can be reduced. These stresses lead to a tube having unexpectedly different and deteriorated properties compared to other products molded from the same polymers under significantly less stringent molding conditions.

Additional stresses are introduced into the tubes when they are filled with the product, and then pressed and welded by heat welding or ultrasonic welding. This method involves bending the "open" end of the tube to itself at an angle of 180 ^o to form a bend at the edge of the weld. This bend extends in the direction of the polymer flow, which, as it turned out, is the direction of maximum weakness of the molded product. This “bending and welding” zone, in which it is necessary to deform the tube to obtain a weld, is that zone obtained by injection molding of the tube, which in practice is susceptible to cracking and bending under stress and as a result of bending.

 The following examples illustrate the specific problems of injection molding such tubes. With the DuPont 2020T polymer described by DuPont as “especially suitable for injection-molded closure and extrudable tubes that require flexibility and maximum resistance to cracking under environmental stress.” These tubes were molded with great difficulty, because in order to simply fill the mold with 2020T polymer, very high specific injection pressures and temperatures were required. Significant degrees of shear and / or bending of the rod were noted during each molding, undoubtedly caused by exceptionally high specific injection pressures. In addition, it was noted that the tubes, in fact, did not have resistance to bending in the direction of the flow of material, and after five extrusion of the tubes manually, significant cracking occurred. The same tubes were tested for cracking under the influence of environmental stress and, despite claims of "maximum resistance" to cracking under the influence of environmental stress, they were found to be completely inconsistent with the molding of thin-walled tubes by injection molding.

As another illustration of the difficulty of injection molding tubes, we note that the Dow 'Dowlex' LLPDE brochure acknowledges that linear low density polyethylene (LLDPE) has significantly better environmental stress cracking (SRNOS) properties than equivalent low density polyethylene and high pressure (LDPE high pressure). To illustrate the difference in the brochure, it is stated that in one comparative test, the high-flowing LLDPE 'Dowlex' has an SRNOS in oil 80 times greater than the SRNNOS achieved by high-pressure LDPE with a similar density and MFI (5700 hours compared to 70 hours). It is also indicated that this LLDPE has an SRNOS of about 10 times that of LDPE when immersed in a 10% Teric solution at 50 ^° C (225 hours versus 26 hours). However, in contrast to these observations, the inventors found that when forming such polymers to obtain thin-walled tubes and then testing them for SRNDOS using a specially developed test method for evaluating SRNNOS tubes, and LLDPE 'Dowlex' 2517 from Dow, and LD 8153 ( Kemcor high-pressure LDPE with similar MFI and density), poorly treated in a 10% Teric solution at 50 ^° C, both collapsed within 20 minutes, and this clearly demonstrates their unsuitability for injection molding tubes. This poor result illustrates the very unsatisfactory and difficult nature of the manufacture of injection-molded thin-walled tubes for sale.

To date, the inventors have found that injection molding of flexible thin-walled products having relatively long thin-walled sections is possible due to the choice of polymers used in the injection molding method having a time to failure of more than 10 hours according to the test results in accordance with the following procedure:
a) injection molding of a plurality of preferably at least six strips of polymer mixture, including any post-molding treatment, is intended to produce a finished product having a cross-sectional dimension of 0.65 mm in thickness and 10 mm in width, conditions of the duration of a long flow with a large shear, similar to those intended for use in the manufacture of a flexible thin-walled product, including any post-molding treatment designed to produce a finished product th product having cross-sectional dimensions of 0.65 mm in thickness and 10 mm in width;
b) carry out the bending of the bands on themselves and stitch them with brackets 3 mm from the fold;
c) immerse the curved stripes in a solution of a stress cracking agent such as ethoxylated nonylphenol, for example 10% Teric N9 solution (nonylphenol ethoxylated with 9 moles of ethylene oxide supplied by Orica Australia Pty Ltd.), and support at a temperature of 50 ^o C;
g) examine the strip for signs of cracking, considering any signs of cracking as a defect; and
d) determine the time to failure as the moment when 50% of the bands show signs of cracking.

In accordance with this, the inventors now offer a method of manufacturing thin-walled products, containing the following operations:
1) the selection of a polymer mixture having SRNOS, corresponding to the above definition and exceeding 10 hours,
2) melting the polymer mixture,
3) injection of the polymer mixture into a mold having a cavity, which creates a thin-walled product having a thin section with a thickness of less than 1 mm, and this thin section is essentially continuous for over 50 mm in the direction of flow of the molten polymer mixture in the mold,
4) removing from the mold a thin-walled product molded from a polymer mixture.

 As for the term “substantially continuous,” it will be clear to those skilled in the art that the thickness of the thin section is generally maintained at less than 1 mm, although some deviation arising from the increase in thickness is permissible, for example, when finishing such a product with embossing, texturing or embossing. The term "thickness" refers to the thickness of the layer of the polymer mixture described above, and does not include any additional layers, such as those that may be included in the multilayer structure. In applications where the mixture is foamed, the inventors have in mind the imaginary thickness of the non-foamed material, which can be easily determined by the density of the polymer mixture.

 It should be understood that throughout the following text of the description and claims, the term "polymer mixture" refers to compositions containing at least one polymer and optionally including additional components, such as those described below.

 It should be understood that throughout the following text of the description and claims, the term "copolymer" refers to polymers comprising two or more monomer units.

 Generally speaking, in order to select a polymer mixture suitable for the manufacture of thin-walled products, it is necessary that the polymer mixture has SRNOS meeting the above definition and exceeding 10 hours. Preferably, the polymer mixture has SRNOS greater than 100 hours, more preferably greater than 200 hours, and most preferably greater than 360 hours. When a thin-walled product is a tube or other container used for packaging a composition such as a moisturizer or shampoo, which can be quite aggressive with respect to a thin-walled product, which leads to deterioration of the product’s properties over time, it is necessary to choose a polymer mixture having SRNOS high, so that a thin-walled product molded from this mixture is able to withstand the harmful effects caused by the use, in spite of any deterioration in properties resulting from the aggressive nature of the materials contained within a thin-walled products. When a thin-walled product is used for packaging with a relatively inert material, a lower SRNOS may be acceptable.

 The above SRNOS test can be carried out using a variety of stress cracking agents. A preferred stress cracking agent is Teric N9 (nine molar nonylphenol ethoxylate available from Orica Australia Pty Ltd.), but other nonylphenol ethoxylates can also be used with advantage. Other stress cracking agents may be used and selected based on the desired end application. Other stress cracking agents include mineral oils, cationic surfactants, solvents, and other agents that will be apparent to those skilled in the art.

 The above SRNNOS test is preferably carried out under molding conditions similar to those of thin-walled products. For example, if you intend to obtain a thin-walled product using molding that includes melt flow oscillation techniques, it is preferable to conduct tests on SRNOS on panels obtained from castings molded by melt flow oscillation techniques.

The SRNOS test described above made it possible to select many polymer blends that are suitable for injection molding to form thin-walled products. In a second aspect of the present invention, there is provided a method for injection molding a thin-walled product, comprising the following steps:
1) melting a polymer mixture containing at least one polymer and at least one compatible agent and / or at least one agent that promotes the formation of crystallization centers,
2) injection of the molten polymer mixture into a mold having a cavity, which creates a thin-walled product having a thin section with a thickness of less than 1 mm, while the thin section is essentially continuous over more than 50 mm in the direction of flow of the molten polymer mixture in the mold , and
3) removing from the mold a thin-walled product molded from a polymer mixture.

You can use a huge variety of polymers as the basis of the mixture, which satisfies the above test for SRNOS or acts as mentioned at least one polymer in the second aspect of the present invention. These polymers include olefin homopolymers and copolymers, preferably homopolymers and copolymers of ethylene or propylene with C ₃ -C ₂₀ alpha or beta olefins and / or polyenes, preferably C ₃ -C ₈ alpha or beta olefins, such polymers have a density in the range from very low to very high density (density is in the range of 0.85-0.97 g / cm ³ ). Vinyl terminated ethylene, propylene and butene copolymers and ethylene, propylene and butene copolymers containing more than 50% ethylene, propylene and butene that are copolymerized with comonomers such as methyl acrylates, ethyl acrylates, and acrylic acid are also suitable for use in the present invention. methacrylic acid, ionomers and ABA copolymers of styrene and ethylene and / or butene and styrene. These polymers can be prepared in a huge variety of ways, including high and low pressure methods, and using a wide variety of catalysts such as Ziegler-Natta catalysts and metallocenes, and have molecular structures ranging from linear to highly branched, thus including LDPE, PESP and HDPE. Particularly suitable for use in the present invention are substantially linear linear and branched polyethylenes or polypropylenes, copolymers of propylene and ethylene or one or more alpha olefins, terpolymers (three-link polymers) of ethylene, propylene or one or more alpha olefins (exemplified by Montell's Catalloy polymers), as well as propylene polymers and copolymers made using metallocene catalysts. Other polymers suitable for use in the present invention include polyacrylic acid polymers.

 The inventors have found that plastomers, "substantially linear polyethylenes", metallocene-branched polyethylene copolymers, propylene alpha-olefin interpolymers and metallocene propylene polymers and interpolymers are preferred for use in the present invention in the manufacture of thin-walled products and, in particular, in the manufacture of flexible tub. The main characteristic of plastomers, "essentially linear polyethylenes", metallocene-branched polyethylene copolymers, propylene alpha-olefin interpolymers and metallocene propylene polymers and interpolymers is the distribution of their composition, i.e. homogeneity of comonomer distribution within and between polymer molecules. Plastomers, “substantially linear polyethylenes”, metallocene-branched copolymers, propylene alpha-olefin interpolymers and metallocene propylene polymers and interpolymers are usually prepared using metallocene catalysts, which are known to facilitate the very frequent introduction of comonomer between and along polymer molecules, which they create. Thus, most molecules of a particular plastomer, “essentially linear polyethylenes”, metallocene-branched polyethylene copolymers, propylene alpha-olefin interpolymers of metallocene propylene polymers and interpolymers will have, according to a rough estimate, the same comonomer content, and within each molecule the comonomer will be have a super-random distribution. Ziegler-Natta catalysts usually produce copolymers having a much wider distribution of the composition, in particular, the distribution of comonomers in the polymers thus obtained will vary very widely between polymer molecules, and the distribution within a given molecule will be less random.

US Pat. No. 5,451,450, the data of which is incorporated herein by reference, describes elastomers such as ethylene alpha olefin copolymers (including ethylene, alpha olefin and polyene copolymers) with a molecular weight distribution in the range of ratios M _w / M _{n of} 1.5-30 preferably in the range of 1.8-10, and more preferably in the range of 2-4. In general, elastomeric polymers contain ethylene homopolymers and interpolymers, with at least one C ₃ -C ₈ α-olefin copolymer being particularly preferred. The term "interpolymer" is used here to indicate a copolymer or terpolymer (three-link polymer), etc. That is, to obtain an interpolymer, at least one other comonomer is copolymerized with ethylene. In general, α-olefins suitable for copolymerization with ethylene to form plastomers contain from about 2 to about 20 carbon atoms, preferably from about 3-16 carbon atoms, and most preferably from about 3-8 carbon atoms . Illustrative non-limiting examples of such α-olefins are propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene and 1-dodecene, and the like. Polyene comonomers suitable for copolymerization with ethylene to form plastomers suitable for the present invention generally have about 3-20 carbon atoms, preferably in the range of about 4 to about 20 carbon atoms, and most preferably in the range of about 4 to about 15 carbon atoms. In one particular embodiment, the polyene is a diene which has a range of from about 3 to about 20 carbon atoms and may be a straight chain, branched chain or cyclic hydrocarbon diene. The diene is preferably a non-conjugated diene (a diene without conjugated double bonds). Non-limiting examples of ethylene / alpha olefin plastomers suitable for the present invention include copolymers of ethylene and butene-1, ethylene and hexene-1, ethylene and octene-1, as well as ethylene and propylene. Non-limiting examples of terpolymer plastomers suitable for the present invention include ethylene / propylene / 1,4-hexadiene and ethylene-octene-1 / 1,4-hexadiene.

 Plastomers and “substantially linear polyethylenes” are prepared primarily using metallocene catalysts. In US patent 5281679, the data of which are given here for reference, a method for producing metallocene homo- and copolymers with a wide molecular weight distribution, mainly in the range of 3-30, which have an increased tensile and impact strength compared to polymers obtained with using catalysis according to Ziegler. They are also characterized by the presence of significantly narrower short chain branching distributions and are less extractable by hexane. Such polymers are suitable for use in the present invention.

 In terms of density, plastomers preferred for use in the method of the present invention are comparable to very low density polyethylene (VLDPE) or ultra low density polyethylene (VLDPE), which are also copolymers of ethylene with α-olefins such as butene, hexene or octene . In the General case, they are defined as copolymers of ethylene with alpha-olefins with a density between 0.86 and about 0.915. A method for producing PEONP in general terms is described in European Patent 120503. Plastomers even with the same density as PEONP have significantly different physical properties due to differences in the manufacturing method, mainly in the use of metallocene catalysts. In general, PEONP, in comparison with a plastomer of similar density, has a significantly higher melting point and softening temperature, molecular weight and / or size distribution of more than 3 and a higher degree of crystallinity.

Elastic, substantially linear olefin polymers are described in a number of patents, including US Pat. No. 5,272,236, US Pat. No. 5,278,272, US Pat. No. 5,380,810, US Pat. No. 5,525,695, and US Pat. No. 5,665,800, all of which are incorporated herein by reference. As an example of an elastic, substantially linear olefin polymer, US Pat. No. 5,278,272 describes one type as having a critical shear rate when establishing a surface melt fracture of at least 50% greater than a critical shear rate when establishing a surface melt fracture of an olefin polymer having the same I ₂ and M _w / M _n . These polymers also have a processability index (PO) less than or equal to that of a comparable linear olefin polymer with the same I ₂ and M _w / M _n . Elastic, substantially linear polymers containing ethylene homopolymers and interpolymers with at least one C ₃ -C ₈ α-olefin copolymer are preferred. The term "interpolymer" is used here to indicate a copolymer or terpolymer and the like. That is, in order to obtain an interpolymer, at least one other comonomer with ethylene is copolymerized.

 The term “substantially linear” polymers means that the backbone of the polymer is replaced by long chain branches, the number of which is from about 0.01 to 3 per 1000 carbon atoms, most preferably long chain branches, the number of which is 0.03-1 per 1000 carbon atoms . The term “linear olefin polymer” means that the polymer does not have long chain branches, such as, for example, conventional linear polymers with units of low density polyethylene or high density propylene, obtained using Ziegler polymerization methods (see, for example, US Pat. No. 4,076,698 and 3645992, the data of which are given here for reference).

 The short-chain branching distribution index (CDRC) is defined as the percentage of the mass of molecules having a comonomer content within 15% of the average total molar content of the comonomer. The PCRC of substantially linear polymers suitable for the present invention preferably exceeds about 30%, in particular, exceeds about 50%.

A particular characteristic of the substantially linear polymers of the present invention is a very unexpected yield property, the value of I ₁₀ / I ₂ being essentially independent of the polydispersity index (i.e., M _w / M _n ). This is a difference from conventional polyethylene resins having such rheological properties that the polydispersity index, I ₁₀ / I ₂ , increases. The density of ethylene or ethylene / α-olefin linear olefin polymers in the present invention is generally from about 0.85 g / cm ³ to about 0.97 g / cm ³ , and preferably from about 0.85 to about 0.92 g / cm ³ .

 Essentially linear polymers preferred for use in the method of the present invention have processability substantially similar to that of high pressure LDPE, while having a tensile strength and other physical characteristics similar to those of conventional LLDPE, without the beneficial effects of special adhesion accelerators (e.g. technological additives such as Viton fluoroelastomers supplied by DuPont).

In US patent 5525695 (the data of which are given here for reference) describes a method of manufacturing a "substantially linear polyethylene", which differ in that they have the following characteristics:
A. Density is from about 0.85 g / cm ³ to about 0.97 g / cm ³ .

 B. Melt index (IR) from 0.01 g per 10 min to 1000 g per 10 min.

C. Preferably, the I ₁₀ / I ₂ melt flow ratio is from about 7 to about 20.

D. the distribution of M _w / M _n molecular weight is preferably less than 5, in particular less than 3.5, and most preferably from about 1.5 to 2.5.

 Elastic, substantially linear olefin polymers can be prepared with wider molecular weight distributions by a suitable choice of catalysts for the polymerization process, as described in US Pat. shear stress. In other words, in the general case, the wider the RMM, the higher the engineering and engineering performance at a large shift, and therefore, the better the machinability characteristics. With a wide molecular weight distribution, “substantially linear olefin polymers”, plastomers and metallocene-branched polyethylenes are particularly suitable for the manufacture of tubes by the method of the present invention.

 The inventors have also found that certain types of polymers, preferably unsaturated polymers such as polyvinyl chloride and polystyrene, more preferably polyolefins, and even more preferably plastomers, "substantially linear polyethylene", copolymers of metallocene-branched polyethylene and polypropylene, and most preferably plastomers and polymers of "substantially linear polyethylene" and propylene copolymers having densities between 0.87 and 0.92 and MFIs of more than 10, and most preferably more than 30, can only be added with cp dstv promoting nucleation, as means to improve ESCR tubes, used in the production of tubes suitable for packaging some less aggressive products. However, the addition of compatible polymers, for example polypropylene and polypropylene copolymers, to such polymers, in addition to agents that promote the formation of crystallization centers, leads to a greater overall SRNOS, and in general they are preferred.

It has been found that polymers, and in particular plastomers and substantially linear olefins having I ₁₀ / I ₂ values above normal, which are essentially independent of the polydispersity index (i.e., M _w / M _n ), and metallocene propylene homo- and copolymers are particularly suitable for the manufacture of injection molded tubes and other thin-walled products having good SRNOS and other physical and / or chemical properties. As discussed in US patent 5281679, the data of which are given here for reference, the expansion of the molecular weight distribution of the polymer and, in particular, polyethylene and its copolymers, increases the tensile strength and tensile strength upon impact of products made from it. The main reason for the high I ₁₀ / I ₂ in the polymer is the presence of both high molecular weight (MM) molecules and low MM molecules in the polymer. It is believed that the fraction of molecules with a high MM contributes significantly to the improvement of the properties of the SRNOS of the polymer, while the proportion of molecules with a low MM contributes to the improved processability of the polymer because of the shear sensitivity of the polymer, thereby making it possible to form the polymer to produce tubes, despite the obvious low engineering (usually measured as I ₂ ) polymer.

High I ₁₀ / I ₂ polymers suitable for the present invention can be prepared in a variety of ways. These methods include the following operations:
1) thoroughly mixing two or more polymers having different molecular weights in suitable mixing equipment,
2) obtaining bi - or multimodal polymers with high I ₁₀ / I ₂ through the "double" reactors and
3) obtaining bi- or multimodal polymers with high I ₁₀ / I ₂ in a single reactor using suitable catalysts.

Catalysts for the production of bi- or multimodal polymers with high I ₁₀ / I ₂ can be selected to obtain the following materials:
1) polymers with a wide molecular weight distribution (for example, with a molecular weight distribution in the range of 3-30, as described in US patent 5281679, referred to here for reference); or
2) essentially two or more polymers, each of which, if necessary, has either a narrow or wide molecular weight distribution. US Pat. No. 5,539,076, the data of which is incorporated herein by reference, describes a method for manufacturing bi- or multimodal polymers with densities between 0.89 and 0.97 in a single reactor.

 Other injection molded polymers are silane grafted or copolymerized polymers. Such polymers can be crosslinked during subsequent processing, which results in formable and / or processable (process) compounds of the crosslinked polymer that provide easy processability, structural and / or technological flexibility of the polymers with relatively low viscosity, while achieving the ultimate strength and other advantages of crosslinked polymers and higher viscosity copolymers. There are numerous patents that describe various aspects of a process for preparing and crosslinking various silane-based compositions that can be used in the present invention. These include US patents 5055249, 4117063, 4117195, 4413066, 4975488 and 3646155, the data of which are for reference.

 In yet another aspect of the present invention, there is provided a compound in which all of the ingredients can be mixed in one step in an extruder just prior to injection molding. A compound consists of one or more types of polymers, such as acrylates or branched, metallocene-catalyzed ethylene alpha-olefin plastomers, which react with an organosilane compound, such as vinyltrimethoxysilane, in the presence of a peroxide, such as dimethyl peroxide, to produce a silane grafted polymer, the treatment being the time of this interaction occurs in the drum of the injection molding machine. Then, just before the silane grafted polymer is injected into the mold, a catalyst, such as dibutyltin dilaurate, is introduced into the silane grafted polymer in the drum of the injection molding machine and mixed to ensure that the catalyst and grafted polymer are thoroughly mixed. The catalyst facilitates crosslinking of the silane compounds in the main chain of the polymer after molding in the presence of moisture by condensation of hydrolyzable silane groups on the main chains of different polymers, thereby producing a new polymer that has properties that are a combination of the properties of individual polymers from which silane grafted polymers are obtained as well as properties imparted by higher molecular weight polymer molecules resulting from the aforementioned crosslinking. The final properties of the new polymer can be changed by changing the proportions of different polymers, changing the nature of any of two or both polymers (for example, by using polymers with additional functional groups, such as vinyl acetate, and / or changing the properties of a silane-containing polymer, for example, by changing the type of polyethylene and / or type of silane chemically bonded to the polymer). The final properties can also be changed by adding other compounds and / or additives, such as fillers, plasticizers and antioxidants, which are well known to any person skilled in the art of polymer blending.

 An alternative method for preparing silane grafted polymers suitable for use in the present invention is to graft a silane to one polymer in the presence of a peroxide or other free radical generator in a suitable reactor, such as an extruder, in a separate step, and pack the resulting grafted polymer into moisture resistant packaging for later use. If necessary, the grafted polymer can be introduced into the injection molding machine along with a suitable amount of a condensation catalyst, the two components being thoroughly mixed in the injection molding machine and then injection molded and crosslinked during the subsequent processing.

 The silane-containing polymer typically contains between 0.1 and 15% hydrolyzable silane. Hydrolyzable silanes, the most widely used in the preparation of silane-containing polymers, are vinyltrimethoxysilane, vinyltriethoxysilane, but this can be any hydrolyzable silane that can be introduced into another polymer to form a silane-containing polymer.

The at least one compatible agent mentioned is preferably a polymer, and when mixed with at least one polymer, mixtures are obtained having such properties that they are, if used after mixing, to form thin-walled products, such as flexible, obtained by injection molding by molding tubes, superior to the original components or pure polymers. The said at least one compatible agent can be selected from the group consisting of ethylene vinyl acetate, ethylene vinyl alcohol, plasticized polyvinyl acetate and polyvinyl alcohol, alkyl carboxyl substituted polyolefins, copolymers of organic acid anhydrides, copolymers containing epoxy groups, chlorinated polyethylene, propylene, copolymers etc., ultra low density polyethylene, very low density, low density, medium density and high density, polypropylene, olibutylene and their copolymers, esters of polyesters, esters of polyesters (for example, the Hytrel series of DuPont), copolymers of acrylonitrile and methacrylate, block copolymers having end blocks of styrene, polyesters, grafted amino and alkoxysilane, vinyl polymers block copolymers of styrene and butadiene, acid grafted polyolefins, vinyl pyrrolidine grafted polyolefins, dihydrite monomers, copolymers unsaturated ester grafted block copolymers, modified x polyolefins containing amide, epoxy, hydroxyl or C ₂ -C ₆ alkoxyl functional groups and other compatibilizing agents suitable for use with polyolefins, particles coated with any of the aforementioned agents, and mixtures thereof. In the aforementioned compatible agents, the functional groups are mainly incorporated into the modified polyolefin as part of an unsaturated monomer that is either copolymerized with an olefin monomer or grafted onto a polyolefin to form a modified polyolefin.

 Alkylcarboxyl substituted polyolefins may include substituted polyolefins in which the carboxyl groups are derivatives of acids, esters, anhydrides and their salts. Salts of carboxylic acids include neutralized carboxylic acids and are often referred to as ionomers (e.g. Surlyn). Typically, acids, anhydrides and esters include methacrylic acid, acrylic acid, ethacrylic acid, glycidyl maleate, 2-hydroxyacrylate, diethyl maleate, maleic anhydride, maleic acid, dicarboxylic acid esters, etc. Preferred examples include ethylene unsaturated carboxylic acid copolymers such as polyethylene methacrylic acid and polyethylene acrylic acid and their salts.

 Organic acid copolymers and anhydrides include maleic anhydride copolymers as well as cyclic anhydride copolymers.

 Compounds of poly-2-oxazoline and fluoroelastomers are also suitable for use as compatible agents. It is preferable to administer poly-2-oxazoline compounds in an amount of 1-40%, most preferably 2-20%. These compatible products increase the adhesion of the polyethylene mixture (PE mixture) to various substrates, which makes them suitable for printing or labeling. The compatibilizer contains an alpha-olefin copolymer substrate grafted with some amounts of aromatic monovinylidene polymer. The alpha olefin copolymer substrate is preferably a terpolymer (three unit polymer) of ethylene, propylene and a non-conjugated diolefin (diolefin without conjugated double bonds).

 Many ethylene copolymers are also used as compatible agents in the process of the present invention. For example, polymers catalyzed in one position, such as metallocene-catalyzed polyethylene, can be used as compatible agents in the present invention.

 Polypropylene suitable as compatible agents may include sidiotactic and atactic propylene and syndiotactic propylene with different melt flow indices, densities and degrees of crystallinity, which can provide different properties in products formed by the method of the present invention. In particular, after mixing with low molecular weight plastomers, a huge number of propylene polymers having a very wide range of MFIs (1-200 +), densities and degrees of crystallinity will yield mixtures suitable for use in the method of the present invention.

 Polyethylene suitable as compatible agents for use in the method of the present invention may include polyethylenes with different melt flow indices, densities and degrees of crystallinity, which can provide the desired properties in the articles obtained by the method of the present invention. This includes polypropylene of very low, low, medium and high density. In particular, this occurs in the case of mixing with low molecular weight plastomers, essentially linear polyethylene and metallocene-branched polyethylene polymers. A huge number of polyethylene polymers having a very wide range of melt flow indices (1-200 +), densities and degrees of crystallinity will give mixtures suitable for use in the method corresponding to the present invention.

 Many monomers were copolymerized with propylene to form propylene copolymers. Many of these copolymers are suitable as compatible agents for use in the present invention. Examples of ethylene-propylene copolymers include Montell's SMD6100P and XMA6170P. Additional examples of polypropylene copolymers are Catalloy KS-084P and Catalloy KS-357P from Montell - these products are considered terpolymers of propylene, ethylene and butene. Other such copolymers and / or terpolymers may also be used.

 Ionomers provide specific advantages as compatible agents when combined with plastomers, essentially linear polyethylene and branched polyethylenes as the aforementioned at least one polymer. Ionomers are usually copolymers of ethylene and acrylic or methacrylic acids, which are neutralized by ions of metals such as sodium, lithium or zinc. An example of one group of ethylene copolymers called ionomers is the commercial product Surlyn (manufactured by DuPont). Ionomers tend to behave similarly to crosslinked polymers at room temperature, and since they are thick and viscous, they can also be processed at elevated temperatures. In particular, a mixture of plastomer and ionomer is preferred, since such mixtures provide polymers with enhanced barrier properties.

 Block copolymers of dihydrite monomers may include block copolymers of dihydrite phenolic monomers, a carbamate precursor, and a polypropylene oxide resin.

 A compatible agent is used in an amount at least sufficient to increase the resistance of the polymer mixture to cracking under the influence of environmental stress. Standard tests for resistance to cracking under the influence of environmental stress are of little importance in determining how specific polymer mixtures will perform their functions in the manufacture of thin-walled products, such as tubes. Not intending to be bound by theory, the inventors nevertheless believe that injection molding of thin-walled products, such as tubes, introduces special stresses in castings and helps to maintain these stresses. The degree and orientation of stresses in products, such as injection molded tubes, leads to their susceptibility to cracking under the influence of environmental stress. Therefore, in order to demonstrate an increase in resistance to cracking due to environmental stress resulting from the present invention, the above test was performed.

 In some formulations, 2% or less of a compatible agent is sufficient to increase the resistance of the polymer mixture to cracking under environmental stress compared with the resistance of the plastomer to cracking under the influence of environmental stress.

 The compatible agent can also be used in amounts exceeding those necessary to improve the compatibility of the polymer mixture in order to optimize the molding characteristics of said polymer mixture and / or the basic properties of the molded article, such as softness and flexibility. Typically, a compatible agent is used in an amount of from about 2 to about 98 wt. % of the polymer mixture, although smaller amounts may be used in some polymer blends. The optimal amount for a particular composition will depend on the required properties and can be determined experimentally. In addition, it was found that the inclusion of percentages of a compatible agent, which are greater than necessary to increase the resistance of the polymer mixture to cracking under the influence of environmental stress, will often provide an improvement in the properties of the polymer mixture, such as tensile strength at break and impact, barrier properties , processing environment and product feel. For example, the introduction of percentages of polypropylene, which are more than necessary to increase the resistance of the polyethylene mixture to cracking under the influence of environmental stress to the required level, can increase the chemical resistance and reduce the transfer ratio of water vapor and water for this polymer mixture in comparison with polymer mixtures containing a minimum the amount of polypropylene necessary to increase only resistance to cracking under the influence of environmental stress. It has also been found that the inclusion of percentages of a compatible agent that are larger than necessary may allow for the introduction of larger percentages of other polymers than would otherwise be acceptable in connection with the present invention. Thus, the use of a compatible agent in such amounts can provide the introduction of more significant than otherwise possible percentages of preferred substantially incompatible other polymers, such as nylons and ethylene vinyl alcohol (EMU), with concomitant improvements in properties such as the limit tear and impact strength, barrier properties, chemical resistance and sensation from the product.

Barrier resins may be added to the polymer blends of the present invention. Barrier resins that can improve compatibility with the at least one polymer include the following: condensation polymers such as polyamides, polycarbonates, and various esters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBTF), polyethylene naphthalate ( PENF), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), ethylene vinyl alcohol (EMU), polyvinyl alcohol (PVA), ethylene vinyl acetate (EVA), EMA, EMAA and EEA, ionomers, vinylidine polymers and copolymers of aromatic series, , propylene and butylene, chlorosulfated polyethylene, polyisoprene and polychloroprene, ether polyalkalenephenylene ether, phenyl formaldehyde, polyacrylate, ethers of polyesters, copolymers of acrylonitrile and methacrylate, copolymers of nitrile, polyacrylonitrile, polyurethane and polyacetan. It should be recognized that some barrier polymers will be more or less compatible with said at least one polymer than others. For example, EMUs with a relatively low ethylene content will be substantially incompatible. The barrier properties of the polymer blends of the present invention can also be improved by the addition of additives capable of interacting with
harmful chemicals, such as oxygen or other gases, or absorb them.

 The polymer mixture may also include many other additives. Examples of additional additives also include polymers, pigments, paints, fillers, antioxidants, plasticizers, UV protectants, viscosity modifiers, additives that can interact with harmful chemicals such as oxygen or other substances, released from the mold, or absorb them, and among other means - melt strength modifiers. These additives can be introduced into one or more components of the polymer mixture or into the polymer mixture as a whole before molding to change its properties so that they satisfy special applications or contribute to the achievement of specific effects on the final product.

 In order to obtain the required barrier properties using a substantially incompatible polymer and without reorienting the polymers before injection molding, it is preferable that the dispersed phase melt index is slightly larger than the continuous phase melt index at the same shear rate. In particular, the barrier resin (usually the dispersed phase) preferably has a melt flow index in such a range that it is 1.1-3.5 times greater than the melt flow index of the continuous phase.

 It is believed that with optimal barrier properties, the droplets of the dispersed phase should be deformed, forming sheets (layered structures) when they are exposed to stresses inherent in the injection method. However, if the melt flow index of the dispersed phase is much lower than the melt flow index of the continuous phase, then the droplets of the dispersed phase will tend to resist deformation, rather than form the layered structure necessary for optimal barrier properties. On the other hand, if the melt flow index of the dispersed phase is greater than the melt flow index of the continuous phase, then there will be a more stable tendency to rupture under the action of shear stress during mixing, which leads to finer dispersion, and hence to smaller sheets of barrier material, thus reducing the efficiency of the barrier. It is also preferable to subject the polymer mixture, including the barrier polymer, to a more prolonged mixing before molding than necessary to obtain a homogeneous mixture. Excessive deviation can lead to reduced barrier properties. One skilled in the art will be able to determine the required amounts of the ingredients of the mixture necessary to achieve a balance of properties. An additional advantage of the formation of layered structures in the polymer blends of the present invention is the ability to design the mold in such a way as to facilitate the flow of the molten polymer through the mold and also directly below the core. It is believed that this mold design facilitates the biaxial stretching of barrier materials to form layered structures that further improve the barrier properties of molded products.

 Another way in which the layered or multilayer structure of the polymers for use in the present invention can be facilitated is to pre-arrange the polymers of the mixture in the form of a composite stream and inject the said stream into a mold to form articles consisting of generally separate, generally planar and parallel layers. This can be achieved in a variety of ways, including co-extruding the composite stream of separate, mostly flat and parallel layers of the various polymer components of the blends of the present invention, and, if necessary, manipulating this composite stream to form a second composite stream having an increased number of layers, essentially the same thickness, and subsequent injection molding of the final stream to form a multilayer plastic product.

 In a particular preferred embodiment of the present invention, the polymer mixture comprises at least one plastomer and at least one ionomer. These polymer blends may preferably include an additional polymer that affects the barrier properties of the blend.

 For example, the inclusion of nylon in such a mixture and the selection of suitable mixing and molding conditions significantly reduces the hydrocarbon and gas permeability of the plastomer. It is believed that a high degree of directional orientation due to the molding process contributes to the highly desirable barrier properties that can be imparted by the addition of nylon and other substantially incompatible polymers. The nylon itself needs to be stretched and oriented to form layered structures in order to optimize the barrier properties. By incorporating nylon into the mixture of plastomer and ionomer, this mixture can be injection molded to form components having barrier properties that are believed to be acquired from nylon, while maintaining resistance to cracking under environmental stress.

 Not intending to be bound by theory, the inventors nevertheless found that the said at least one polymer has the property of being able to interact with the said at least one compatible agent, due to which the properties as of the aforementioned at least of one polymer, and of the at least one compatible agent mentioned, change significantly and unexpectedly, making the polymer mixture thus prepared suitable for the manufacture of thin-walled products.

It is believed that the interaction between said at least one polymer and said at least one compatible agent creates regions within the molded articles that may be called “compounds”. It has been found that these “compounds” absorb or distribute stresses in products made from a polymer mixture. It has been found that the presence of these “compounds” enclosed within the product causes absorption or dissipation of stresses, which would otherwise lead to poor physical properties. It is assumed that these so-called “compounds” result from the presence of one or more of the following mechanisms:
a) the polymer and a compatible agent interact, which leads to an increase in the number of amorphous zones within the polymer;
b) the interaction between the polymer and a compatible agent leads to a significant localized decrease in the degree of crystallinity, i.e. the appearance of relatively amorphous regions on the interface between the polymer and a compatible agent; and
c) the interaction between the polymer and a compatible agent, which, although it does not lead to a reduced degree of crystallinity, and therefore to the appearance of more amorphous regions, nevertheless creates a region on the interface between the polymer and a compatible agent, which has an increased ability to absorb or distribute stresses .

 In particular, it was found that when said at least one polymer is an ethylene homo- or copolymer, and preferably a plastomer or substantially linear polyethylene, said polymer is capable of reacting with propylene and many of its copolymers, and the crystallinity of said polymer is reduced. It is believed that propylene polymers act as crystallization promoting agents for said at least one polymer, and the number of amorphous zones inside said at least one polymer increases. But analysis by differential scanning calorimetry (DSC) shows that they also act, significantly reducing the overall crystallinity of the ethylene polymer and, in particular, plastomers and essentially linear propylene polymers. It is also believed that these amorphous regions, along with the effects on the interface between the at least one polymer and the propylene polymer, act by reducing or distributing the stress introduced during the molding process in the molded part, thereby reducing SRNOS. At the same time, said at least one polymer interacts with said at least one plastomer or substantially linear polyethylene, while significantly reducing the degree of crystallinity of said at least one plastomer.

 It is believed that many of the polymer blends form a continuous continuous layered structure and that the interface between the at least one polymer and the at least one compatible agent is characterized by uniform mixing of this at least one polymer and this, according to at least one compatible agent at the microscopic level. In other words, it is believed that at least one compatible agent is effective. as an interacting filler. It is believed that due to this uniform mixing between the at least one polymer and the at least one compatible agent, the overall properties of the polymer mixture are improved. In particular, when this at least one polymer is low molecular weight plastomers and essentially linear polyethylenes, the compatibility of other polymers previously mentioned as being essentially incompatible with polyethylene can now be improved, and mixtures thereof have a range of properties, which provides a commercially acceptable manufacture of products that to date have not been commercially acceptable.

 It has been found that many compounds known to be capable of forming crystallization centers of polymers, in particular olefin polymers and copolymers, especially ethylene polymers and copolymers, improve the properties of SRNOS polymers for use in the present invention. Depending on the nature of the individual polymer (s), the compatibilizing agents themselves (i.e., without the addition of compatible agents) are able to increase the SRNOS of this polymer (these polymers) to a level that allows this polymer (these polymers) to be used in the manufacture obtained by molding tubes. It is believed that agents that promote the formation of crystallization centers increase the AVER of polymers in the manufacture of tubes, since they cause the formation of a larger number of small crystals than would otherwise be possible. This larger number of small crystals leads to an increase in the number of amorphous zones within the polymer that are capable of absorbing or dissipating the stresses introduced into the castings of the tubes during injection molding, thereby increasing the SRNOS of the product and its resistance to bending. Compounds that promote the formation of crystallization centers and are suitable for use in the present invention include inorganic compounds such as talc, mica, compounds of various metals such as oxides and silicates, as well as various organic compounds, including various paints and pigments. However, for most of the beneficial results in the injection molding of tubes, it is preferable to use means that promote the formation of crystallization centers, together with compatible polymers.

Compounds known to be capable of decreasing the glass transition temperature (T _c ) of the aforementioned at least one polymer of the present invention, in particular olefin polymers and copolymers, and especially ethylene polymers and copolymers, have been found to improve the properties of SRNOS polymers for use in the present invention. Depending on the nature of a single polymer (individual polymers), agents that reduce T _s themselves (that is, without the addition of compatible agents, agents that form crystallization nuclei, or "agents for providing high thermal density") can increase the SRNOS of this polymer (these polymers) to a level that allows the use of said polymer (said polymers) in the manufacture of tubes formed by molding. It is believed that agents that reduce T _c increase the AVER of polymers in the manufacture of tubes, since they effectively increase the time it takes for the polymer to cool to its crystalline state, thereby increasing the amount of time available to rearrange the polymer molecules themselves in order to reduce stresses introduced in the process molding. This results in a molded part having lower stresses introduced during molding than if T _c had not decreased, and thus a molded article having an increased SRNOS is obtained. A suitable T _c reducing agent is polypropylene. However, for most of the beneficial results in the injection molding of tubes, it is preferable to use means that reduce T _s , together with compatible means, if the means that reduce T _s is not itself a compatible means.

 Compounds of poly-2-oxazoline and fluoroelastomers are also suitable for use as compatible polymers. Administration of poly-2-oxazoline compounds in an amount of 1-40%, most preferably 2-20%, increases the SRNOS of the polymers (see US Pat. No. 4,474,928). These compatible polymers also increase the adhesion of the PE mixture to various substrates, which makes them useful for preparing PE for printing or labeling.

Although the effects of increased SRNOS introduced by additives, such as agents that promote the formation of crystallization centers, and agents that reduce T _c , may not be noticeable, in particular in “ordinary” castings, it is still believed that in castings such as thin-walled tubes, of which the polymer is subjected to rapid cooling rates, high injection speeds, high specific injection pressures, long narrow paths and flow radii (and resulting from high levels of introduced stresses), these effects can be significant even at low levels of addition. It has been found that such additives can increase the SRNOS of some polymers to such an extent that the at least one polymer and a sufficient amount of one additive can be suitable for injection molding.

 In accordance with a further aspect of the present invention, said at least one compatible agent may be included in said at least one polymer. For example, a polymer having monomers including compatibility enhancing groups can be copolymerized with other monomers to form a polymer with improved compatibility. For example, a monomer having a methacrylic acid group can be added to the polymerizable mixture of said at least one polymer to form a plastomer with improved compatibility. Alternatively, the compatibility improver group may be grafted onto the polymer. The polymer to which the compatibilizing group is grafted is advantageously a plastomer or a substantially linear polyethylene.

 The polymer mixture can be obtained by extruding some or all of the components of the polymer mixture and using the resulting finely divided extrusion mixture in the injection molding method of the present invention. Alternatively, it is possible to obtain a polymer mixture in the form of its components and to mix before melting the polymer mixture and during this melting in the proposed method.

 The polymer mixture can be melted by any convenient means. In particular, it is convenient to melt the polymer mixture in a conventional injection molding machine, where a screw rotating in a heated drum melts the polymer mixture and injects the molten polymer mixture into a mold. Products molded from a polymer mixture can be easily removed from the mold using conventional means.

 The injection molding method according to the present invention makes it possible to produce injection molded articles having surprisingly thin sections and at the same time preserving the mechanical properties of the polymer mixture. The inventors have found that injection molding can produce products having thin cross sections ranging in size from 0.3 mm to 0.7 mm, and such thin-walled products can have thin walls longer than 50 mm. These products can be easily manufactured without significantly compromising the mechanical properties of the plastic.

 The polymer blends of the present invention, which allow injection molding of articles having thin sections, provide a number of advantages that have so far been unattainable due to technical limitations. These technical limitations are best demonstrated in the production of thin-walled tubes. These tubes, which are very important from a commercial point of view, are extruded, which causes the use of regulation and changes in wall thickness in order to obtain the possibility of manufacturing tubes having an adjustable and variable wall thickness. The present invention provides for the manufacture of products having thin sections, with the possibility of obtaining an adjustable and variable wall thickness in these thin sections. For example, in a particular embodiment of an injection molded tube, the wall thickness of the tube may vary along its length. The wall thickness may be greater in the neck of the tube, thus providing increased flexibility towards the end. The present invention also provides for the incorporation of prints into the thin walls of a tube. Imprints can take the form of company logos, brands, various text, as well as textures or surface finishes, such as skin texture or waviness.

 An additional advantage of the present invention, which until now was unattainable due to technical limitations, is the use of the marking "in the process of molding" for decorative finishing of thin-walled tubes. Extruded tubes should not be subjected to decorative finishing by marking during molding, as a result of which any marking of such tubes has to be carried out as a separate and expensive technological operation. Tubes made in accordance with the present invention can be labeled during the molding process in a one-step molding process, thereby avoiding a separate and expensive process step. The placement of the tubes in the cavity can be accomplished using a variety of means, including placing the label on the core when the mold is open, closing the mold and transferring the label from the core to the cavity using a variety of means just before the polymer is injected to form the tube marked during molding.

 An additional advantage of the present invention is the possibility of applying a barrier sheath to the entire rod or part thereof before forming said barrier sheath, which is transferred to the molded product during molding to impart improved barrier or other beneficial properties to the tubes made in accordance with the present invention. An additional advantage of the present invention is the possibility of coating either the core or the cavity of the mold, or both of these structural elements prior to molding, followed by transfer of the coating during molding to a suitable surface of the molded product. This process results in a coating on either the outer or inner surface of the tubes manufactured in accordance with the present invention. Such coatings can have many functions, including decorative or barrier.

 The present invention, which provides injection molding of thin-walled products, also provides many changes in the shape and configuration of products, which have so far been limited due to technical difficulties in the manufacture of thin-walled products. And again, bearing in mind the example of a thin-walled tube, a lot of plugs, hooks or hinged lids with latches can be introduced into the design. Until now, the introduction of such structural elements required the manufacture of such additional elements and their subsequent welding or attachment to tubes in a different way, with a significant increase in the total cost of the tube. In accordance with the present invention, the use of appropriate tool designs and / or dual injection molding equipment allows for the one-step manufacturing of tubes having built-in plugs, hooks, snap-on hinges or other additional elements formed from the same or different polymers.

 A number of modifications can be made to standard tools for the manufacture of tubes to facilitate the manufacture of unitary tube castings with additional elements, in particular, unitary tube castings with corks. Such castings of unitary tubes with corks, if necessary, can have a huge number of loops (including working loops), dosing marks and other convenient features obtained in any way during the molding process. In cases where the polymer used to form the unitary tube with the cork is not rigid enough to allow the formation of a conventional loop with a "self-closing" or "snap" mechanism, the loop itself can be designed with a radius of curvature. Provided that the polymer has sufficient elasticity, this radius in combination with the elasticity of the polymer should affect the self-locking of the cork.

 An additional advantage of the method corresponding to the present invention is that the possibility of manufacturing tubes with special circuits designed to accommodate fasteners provides a relatively inexpensive and easy fastening of convenient structural elements, such as self-sealing valves. A typical set of tube and self-sealing tube consists of at least four, and often five separate structural elements consisting of two tube parts (tube body and head with shoulders), tube body, self-sealing valve, fixing devices for attaching the valve to the body and, often, a protective element for a valve designed to prevent the release of contents, in particular during packaging and delivery to retail outlets. This self-sealing plug consisting of at least three parts is assembled separately and then attached to the tube. The method according to the present invention provides for the manufacture of a one-piece tube with a valve receptacle and a hinged upper protective element to which the valve and the fixing device can be easily attached. This reduces the number of parts that need to be manufactured, as well as the complexity and number of steps of the assembly method. This greatly reduces the cost of such tubes with plugs.

 In a further specific embodiment, the use of at least one compatible polymer in accordance with the present invention allows the manufacture of articles, such as tubes, which may have protective or barrier coatings applied directly to internal and / or external thin-walled areas without the need for pre-treatment, such as corona discharge pretreatment or fire pretreatment. For example, the administration of polyoxazoline compounds can improve the adhesion of polishes and varnishes to such an extent that such pretreatment is no longer necessary. This may be a specific advantage in the case of containers for food use or for the content of substances, the conclusion of which in containers requires special coatings.

 Alternatively, suitable barrier and other coatings can be applied by conventional means, such as immersion, spraying, printing, vapor deposition or vacuum deposition, the latter method being applicable, in particular, for applying materials with good barrier properties, such as oxides and / or nitrides of metals and nonmetals (for example, silicon oxide) or fluorine, as well as carbon and / or organic radicals with useful properties. In addition, some coatings, such as coatings obtained by reacting a polymer of a tube with fluorine, can also interact with monomers containing various beneficial functional groups to further improve the properties of the coatings. For example, hydroxyl-containing monomers can interact with a fluorinated polyethylene coating to form a hydroxyl-containing coating.

 By their very nature, tubes have thin, soft and flexible walls. This lack of rigidity in the molded tubes makes it difficult to push the molded part out of the mold core by conventional mechanical means used for injection and injection molding, and the technological impact on structural elements such as broaching plates and fingers of the injection tool without creating damage to the castings . An additional disadvantage is that low ejection speeds are often necessary to minimize the potential for damage to the ejection tube.

 It was found that the use of compressed gas during ejection minimizes the possibility of damage to the tube during ejection, and also provides quick ejection. After forming the tube in the cavity of the mold and shrinkage of the tube sufficient to be removed from the cavity of the mold, the male and female parts of the mold are separated by sliding the male shaft part with the female part by sliding. At the same time or after that, it is possible to separate the molded tube by injecting compressed gas from the inside of the core portion and providing compressed air to the inner surface of the end portion of the molded tube, most preferably by lifting the rod tip from the main portion of the rod immediately before the air injection to break a seal that often exists between the molded tube and the stem to facilitate simplified removal of the molded tube. This rise of the tip, as well as the injection of pressure under the end part, will ensure the separation of the molded tube and the male rod part by relative sliding of the molded tube along the tip of the male rod part. To facilitate separation, the male rod portion may have an outer surface with a slight taper, so that the diameter of the male rod portion is larger at the end of the tube remote from the end portion.

 In addition, the outer surface of the male rod portion can be molded or machined to provide some degree of surface roughness to prevent the formation of a vacuum seal between the molded part and the male rod portion during pressurized gas injection. That is, this degree of surface roughness will allow compressed air to flow along the outer surface of the male rod portion and slightly expand the molded tube to separate the tube from the rod.

 In a further specific embodiment, in order to facilitate the removal of the molded part from the cavity, compressed gas can be injected into the mold immediately before or during the separation of the rod from the cavity so that gas flows between the outer surface of the molded part and the inner surface of the cavity, thereby the very separation of the molded part from the cavity and its subsequent removal on the core of the mold from the cavity.

 In order to facilitate easier flow of the polymer into the cavity to form a thin-walled product during the injection process, the cavity can be evacuated immediately before the injection or during the polymer injection. Filling the mold can also be facilitated by balancing the flow of polymer within the mold by milling longitudinal and / or transverse grooves in the core or cavity, or both, to guide and / or accelerate said polymer flow into selected areas within the mold.

 The present invention also provides the use of expandable cores in the mold, which facilitates the extraction of thin-walled products from the mold, and also provides the manufacture of thin-walled containers having wide sections adjacent to the head and shoulder region, in a way that has not been possible until now.

The present invention will be described in more detail by means of the following non-limiting embodiments and drawings, in which:
FIG. 1 is a view of a thin-walled container made from a polymer blend of the present invention;
FIG. 2 is a view of a thin-walled container made of a polymer mixture in accordance with the present invention;
FIG. 3 is a view of a thin-walled container made of a polymer mixture in accordance with the present invention;
FIG. 4 is a view of a thin-walled container made of a polymer mixture in accordance with the present invention;
FIG. 5 is a view of a thin-walled container made of a polymer mixture in accordance with the present invention and including a hook molded as a unit with this container;
FIG. 6 is a view of a thin-walled container made of a polymer mixture in accordance with the present invention and comprising a flange with an opening adapted to hang the container on a hook or bracket during a sale;
FIG. 7 is a view of a thin-walled container made of a polymer mixture in accordance with the present invention and comprising a hook adapted to hang the container on a hook or bracket during a sale;
FIG. 8 is a sectional view of a thin-walled container made of a polymer mixture in accordance with the present invention and comprising a barrier coating on the inner surface of the container;
Fig.9 is a view of a unitary tube with a stopper;
FIG. 10 (a) and 10 (b) depict views of a tube with a side pocket for containing items such as food samples, toothbrushes, or combs;
FIG. 11-14 - the details of several load-bearing mechanisms for unitary tubes with additional elements and, in particular, unitary tubes with plugs.

Some of the structural modifications of the molds that can be used for molding castings of unitary tubes with additional elements are shown in Figs. 11-14. In these designs:
1 - gate run for molten polymer;
2 - hinged closure "snap-on"cover;
3 - clapper disk valve;
4 - a core;
5 - valve stem - "crackers"(3);
6 - side wall of the tube;
7 - working loop;
8 - channels and / or grooves for improved polymer flow to the side walls of the tube;
9 - groove for improved drainage of the polymer to the side walls of the tube;
10 (a) - the support located on the disk valve (3);
10 (b) —the support shown in the retracted position;
11 - locations of supports on the disk valve (3);
12 (a) - supports located both on the shaft (4) and on the disk valve (3);
12 (b) - a support located on the side of the rod;
13 - retractable rod support, depicted in the extended position;
14 - location of the support on the covering part of the mold;
15 is a retractable rod support shown in an unextended position.

For cases of unitary tubes with additional elements, when the rod does not bend or the rod moves laterally if the rod is not supported (for example, in large diameter tubes made of materials with a high melt flow index), Fig. 11 (a) shows a longitudinal a section of a mold with an uncracked core configured to produce a unitary tube with a stopper. FIG. 11 (b) shows a sectional plane along line XX shown in FIG. 11 (a), and FIG. 11 (b) shows an embodiment of section XX, which is an alternative to section YY shown in FIG. 11 ( a). In a further refinement of the basic design of the tool, this tool may have a slot along the line XX ₁ (or XX ₂ ) so that the part of the tool limited by lines XX ₁ (or XX ₂ ) and YY can be separated from the part of the tool limited by lines X -X and ZZ. It can be replaced by an alternative part of the tool, limited by lines XX ₁ (or XX ₂ ) and YY (see Fig. 11 (c)), including another design or kind of cork, made with the possibility of manufacturing a tube with a different cork. The same principle can be extended to other types of additional elements. The possibility of a simple modification of this general tube design by means of “interchangeable parts” for molding tubes with many other fasteners also provides, if necessary and with the corresponding “interchangeable parts”, molding tubes without fasteners, i.e. "standard" tubes with a "head and shoulders."

 For cases of unitary tubes with additional elements, when there is a possibility that the rod will bend if the rod is not supported, a number of designs are able to stabilize the rod from lateral movement (and therefore, from obtaining a changing wall thickness), while simultaneously forming a unitary tube with additional an element.

 12 shows a tool structure in which the rod is stabilized against bending by applying one or more supports protruding from the top of the female half of the mold and pressed into the popping valve located on the shaft of the male part of the mold during injection of the polymer to form products. Immediately after the polymer is injected to fill the mold, but before the drum valve is closed, the supports are raised to allow the polymer to flow into the gaps left by the supports, thereby guaranteeing the formation of a perfect cast. 10 (a) denotes a support located on the flapper of the rod, and 10 (b) indicates a support raised to allow the polymer to flow into the gaps left by the support. In a suitable case, you can place the support in the "zone (11) location of the supports." 12 (b) is a sectional plane along line XX showing a series of support zones on a clapper valve.

 13 shows a tool structure in which the rod is stabilized against bending by applying one or more supports (12 (a) and 12 (b)) that protrude from the cavity to support the rod from the side during polymer injection to form the article. The advantage of the support 12 (b) is that it also firmly presses the disk valve (3) against the shaft (4), thus minimizing the possibility of its lifting under the influence of specific injection pressure. Immediately after the polymer is injected to fill the mold, but before closing the drum valve, the supports are retracted to allow the polymer to flow into the holes left by the supports, thereby guaranteeing the formation of a perfect cast.

 On Fig depicts the design of the tool, in which extendable bearings located inside the rod, extended and rigidly mounted on the covering part of the mold to "anchor" the rod from the lateral movement of this rod. Immediately after injection of the polymer to fill the mold, but before closing the disk valve, the support is withdrawn to allow the polymer to flow into the gaps left by the support, thereby guaranteeing the formation of a perfect cast. A modification of the aforementioned mechanism is to ensure that the entire core protrudes upward to fit into the female mold so that after injection of the polymer to fill the mold, but before closing the drum valve, the entire core is withdrawn, allowing the polymer to flow into the new cavity left by the withdrawn core and thereby guaranteeing the formation of a perfect cast. Another advantage of this design (i.e., placing the rod off-center of the moldable plug) is that there are no restrictions on the center of the plug due to the placement of fixtures. This ensures the formation of rather complex plugs (for example, with vents and membranes that provide an effective "cut-off" of the contents of the tube), such as those designed for several bottles with liquid drugs. In an additional embodiment, the mold can be designed by providing a very thin film applied across the opening of the plug hole to check for capping.

 The main advantages of stabilizing mechanisms, such as those shown in FIGS. 12-14, include the fact that the rod rests and is located “off-center”, thus providing an unshifted injection point with its central location. This allows the formation of “centrally located” additional elements, such as holes and flow control mechanisms, which otherwise would be located “off-center”. If permissible or necessary is the location of the holes or other additional elements "off center", then it is possible to place the support in the center through a number of mechanisms that are well known to practitioners in this field of technology.

Example 1
A polymer mixture prepared from 50% Exact 4038, 20% Catalloy KS059P, and 30% 6100P from Montell was injection molded to form a tube-like container having a body having the form of a continuous cylinder with a diameter of 35 mm and a length of 150 mm and a neck and shoulder section made with the possibility of placing a threaded cap on it. The thickness of the continuous cylinder varied from 0.8 mm near the neck and shoulders to 0.5 mm at the distal end. It was found that the tube-shaped container has properties suitable for use, for example, in the cosmetic industry.

Example 2
A polymer mixture prepared from 60% Exact 4038 and 40% 6100P from Montell was injection molded to form a tube-like container having a body having a continuous cylinder shape with a diameter of 35 mm and a length of 150 mm and a portion of the neck and shoulders that could be placed on it threaded cap. The thickness of the continuous cylinder varied from 0.8 mm near the neck and shoulders to 0.5 mm at the distal end. It was found that the tube-shaped container has properties suitable for use, for example, in the cosmetic industry.

Example 3
A polymer mixture prepared from 24% Exact 4038, 56% Affinity 1350 and 20% Surlyn 9970 was injection molded to form a tube-shaped container having a body having a continuous cylinder shape with a diameter of 35 mm and a length of 150 mm and a neck and shoulder section made with the possibility of placing a threaded cap on it. The thickness of the continuous cylinder varied from 0.8 mm near the neck and shoulders to 0.5 mm at the distal end. It was found that the tube-shaped container has properties suitable for use, for example, in the cosmetic industry.

Example 4
A polymer mixture prepared from 24% WSM 168 (Orica Australia Pty Ltd.), 56% Affinity 1350 and 20% Surlyn 9970 was injection molded to form a tube-like container having a body having a continuous cylinder shape with a diameter of 35 mm and a length of 150 mm and section of the neck and shoulders, made with the possibility of placing on it a threaded cap. The thickness of the continuous cylinder varied from 0.8 mm near the neck and shoulders to 0.5 mm at the distal end. It was found that the tube-shaped container has properties suitable for use, for example, in the cosmetic industry.

SRNOS Test
Six thin sections of the injection molded polymer mixture with a thickness of 0.65 mm were used to determine the resistance to cracking under the influence of environmental stress. Sections with a width of 10 mm were cut in the direction transverse to the main direction of flow of the polymer mixture in the mold, and then processed using some processing options after molding. Each section was bent over itself and stitched with brackets 3 mm from the bend. Curved sections were immersed in a 10% Teric N9 solution at 50 ^° C (Teric is a trademark of Orica Australia Pty Ltd.). Then the strip was subjected to regular monitoring for signs of cracking. Any sign of cracking was considered a defect. The time when 50% of the sites (i.e. 3) were destroyed, called the time until the destruction of the polymer mixture. The test was completed after 360 hours if the polymer had not yet been destroyed.

Comparative Example A
Dow Affinity Plastomer, having a crystallinity of about 34%, was injection molded and six sections of the mold from the mold were cut and tested for SRNOS. The results are shown in table 1.

Examples 5-7
Dow Affinity plastomer, having a crystallinity of about 34%, was mixed with ADP 126 polypropylene (Montell) in the amounts shown in Table 1. These mixtures were injection molded and six sections of the mold from the mold were cut and subjected to a SRNOS test. The results are shown in table 1.

Examples 8-10
A Dow Affinity plastomer having a crystallinity of about 34% was mixed with Surlyn 9970 (DuPont) in the amounts indicated in Table 2. These mixtures were injection molded and six sections of the mold from the mold were cut and tested for SRNOS. The results are shown in table 2.

Example 11
The polymer mixture was mixed from 80% Affinity (34%) from Dow, 19% nylon (from BASF) and 1.2% Surlyn 9970. The polymer mixture was injection molded and six sections of the mold from the mold were cut off and subjected to a SRNOS test. The polymer mixture had a test result on SRNOS 360+ hours.

Examples 12 and 13
A polymer mixture of 79% Affinity (with a crystallinity of about 34%) from Dow and 30% Surlyn 9970 was mixed and injection molded to form a thin-walled tube. The second polymer mixture was mixed from 76% Affinity (with a crystallinity of 24%) from Dow, 20% nylon B3 (from BASF) and 4% Surlyn, and it was injection molded to form a thin-walled container. Thin-walled containers were filled with gasoline and brewed. A polymer mixture comprising 20% nylon and 4% Surlyn showed gas permeability approximately 20 times lower than gas permeability of a mixture containing only plastomer and Surlyn.

Example 14
A Dow Affinity plastomer having a crystallinity of about 34% was mixed with TiO ₂ in the amount shown in Table 3. The mixtures were injection molded and six sections of the mold from the mold were cut and subjected to a SRNOS test. The results are shown in table 3.

 It will be clear to those skilled in the art that the invention described herein can be modified and modified otherwise than specifically described above. It should be understood that the invention covers all such variations and modifications that are within the scope of the claims. The invention also encompasses all steps, features, compositions and compounds mentioned or indicated in this description, individually or in combination, as well as any and all combinations of any two or more of the mentioned steps or features.

Claims (17)

1. A method of manufacturing a flexible thin-walled products, which consists in melting the polymer mixture, injecting the molten polymer mixture into the mold and removing from the mold a thin-walled product molded from the polymer mixture, characterized in that the polymer mixture has resistance to stress cracking environment exceeding 10 hours, determined according to the test results in accordance with the following procedure: a) injection molding of many strips of the polymer mixture, including any post-molding treatment designed to produce a finished product having a cross-sectional dimension of 0.65 mm in thickness and 10 mm in width, under conditions of long flow with a large shear, similar to those intended for use in the manufacture of a flexible thin-walled product ; b) carry out the bending of the bands on themselves and stitch them with brackets 3 mm from the fold; c) immersed the curved stripes in a solution of a stress cracking agent, for example, in a 10% solution of Terik 9, a nonylphenol ethoxylated with nine moles of ethylene oxide, and maintained at 50 ^° C; g) examine the strip for signs of cracking; d) determine the time to failure as the moment when 50% of the strips show signs of cracking, and the mold has a cavity that creates a thin-walled product having a thin section 1 mm thick or less, and this thin section is essentially continuous for over 50 mm in the direction of flow of the molten polymer mixture in the mold.  2. The method according to claim 1, characterized in that the polymer mixture has a resistance to cracking under the influence of environmental stress in excess of 10 hours, when the means of causing cracking under the influence of stress used in tests for the specified resistance is ethoxylated nonylphenol.  3. The method according to claim 1, characterized in that the polymer mixture has a resistance to cracking under the influence of environmental stress in excess of 10 hours, when the means of causing cracking under the influence of stress, used in tests for the specified resistance, is a 10% solution nonylphenol ethoxylated with nine moles of ethylene oxide.  4. The method according to claim 3, characterized in that the polymer mixture has a resistance to cracking under the influence of environmental stress in excess of 100 hours  5. The method according to claim 3, characterized in that the polymer mixture has a resistance to cracking under the influence of environmental stress in excess of 200 hours  6. The method according to claim 3, characterized in that the polymer mixture has a resistance to cracking under the influence of environmental stress in excess of 360 hours  7. The method according to claim 1, characterized in that the polymer mixture has a melt flow index greater than 10, preferably greater than 20, most preferably greater than 30.  8. The method according to claim 1, characterized in that the polymer mixture contains at least one polymer and at least one compatible agent and / or at least one agent that promotes the formation of crystallization centers.  9. The method according to claim 8, characterized in that at least one polymer is selected from the group consisting of plastomers, polyethylenes, ethylene copolymers and one or more unsaturated olefins, essentially linear polyethylenes, branched polyethylenes, polymers and copolymers ethylene obtained using metallocene or other catalysts giving copolymers characterized by a super-random distribution of comonomers within polymer chains, polypropylenes, propylene and ethylene copolymers and / or one or more unsaturated olefins, polymers and copolymers of propylene obtained using metallocene or other catalysts which give copolymers characterized supersluchaynym distribution of comonomers within the polymer chains, lactic acid polymers, silane polymers and mixtures thereof. 10. The method according to p. 8, characterized in that at least one compatible agent is selected from the group consisting of ethylene vinyl acetate, ethylene vinyl alcohol, plasticized polyvinyl acetate and polyvinyl alcohol, alkyl carboxyl substituted polyolefins, copolymers of organic acid anhydrides, copolymers containing epoxy groups , chlorinated polyethylene, copolymers of ethylene, propylene, butylene, etc., ultra low density polyethylene, very low density, low density, medium density and high density polypropylene, polybutylene and their copolymers, esters of polyesters, esters of polyesters, copolymers of acrylonitrile and metal acrylate, block copolymers having end blocks of styrene, polyesters, polyethylene, grafted with amino and alkoxysilane, vinyl adhesion polymers, block copolymers of styrene and butadiene, acid grafted polyolefins, vinyl pyrrolidine grafted polyolefins, dihydrite monomer block copolymers, unsaturated propylene grafted esters, modified poly Léfini Faunal Reserve comprising amide, epoxy, hydroxy or C ₂ -C ₆ alkoxy functional groups, polyoxazoline, fluoroelastomers, other means of improving compatibility of polymers suitable for use with polyolefins, particles coated with any of the aforementioned agents, and their mixtures.  11. The method according to claim 8, characterized in that at least one agent that promotes the formation of crystallization centers is selected from the group consisting of talc, mica, compounds of various metals, such as oxides and silicates, as well as various organic compounds, including various paints and pigments.  12. The method according to claim 8, characterized in that at least one polymer is polyethylene or a copolymer, and at least one compatible agent is a propylene-based polymer.  13. The method according to p. 12, characterized in that at least one copolymer is a linear, essentially linear or branched polyethylene or copolymer, characterized by a super-random distribution of comonomers within the polymer chains, and at least one compatible means is a polymer based on polypropylene.  14. The method according to claim 1, characterized in that the thin-walled product is a tube.  15. Thin-walled tube, characterized in that it is made in accordance with the method according to claim 1.  16. Thin-walled tube according to clause 15, characterized in that it has a unitary design and includes a built-in cork formed in a mold.  17. Thin-walled tube according to claim 15, characterized in that it has a length of 150 mm.

Images