CS261164B1 - Material for injection molding of shoe sole - Google Patents

Abstract

The solution concerns the issue of sole part production. The purpose of the solution is to increase the dynamic stability of material mixtures from which sole parts are produced on injection molding machines. The stated purpose is achieved in particular by the material for the production of soles consisting by weight of 35 to 60% of a suspension polymer of vinyl chloride with a K-value of 55 to 70, softened with 25 to 55% diethylhexyl phthalate, 5 to 25% of a linear butadiene acrylonitrile polymer, mixed with 0.25 to 3.0% by weight of an inert filler in the form of silicon dioxide or calcium carbonate, or powdered polyvinyl chloride, and 2.2 to 13.5% of a stabilizing system with a lubricating effect, facilitating processing on injection molding machines, which stabilizing and lubricating system contains by weight 0.5 to 3.0% of salts of organic fatty acids, in particular oleic, stearic or myristic acids, with combinations of divalent metals Ba-Cd, Ba-Zn, Mg-Zn, Ca-Zn and Ba Cd-Zn, 0.5 to 2.0% alkyl, aryl or alkyl-aryl phosphites in which the alkyl radical is phenyl, 1 to 4% epoxidized soybean oil, 0.01 to 2% low molecular weight polyethylene wax and 0.2 to 2.5% alkyl esters of C3 to C1q fatty acids with a chain length of C12 to C22.

Description

The invention relates to a material for injection molding shoe sole parts containing polyvinyl chloride and butadiene-acrylonitrile copolymer in a weight ratio of at least 2:1, polyvinyl chloride plasticizers, fillers, lubricants, stabilizers, optionally blowing agents such as azodicarbonamide, in an amount of from 0.01 to 5% by weight, based on the material, and initiators for the decomposition of blowing agents.

As is known, mixtures of plasticized polyvinyl chloride modified with acrylonitrile rubber are used in the shoe industry for the production of polyvinyl chloride soles, which require high abrasion resistance, resistance to dynamic stress, especially at low temperatures, and possibly resistance to the effects of oils.

During the injection molding process, the plastic melt is subjected to thermal and shear forces. One of the characteristic features of melts made from acrylonitrile butadiene modified polyvinyl chloride is the high viscosity of the melt, resulting in high shear stress and often uncontrollable temperature development in the machine chamber. To stabilize these mixtures, organotin sulfur stabilizers such as dibutyltin mercaptide, or sulfur-free stabilizers such as dibutyltin dilaurate, have been used. These stabilizers generally, and together with the insufficient quality of the lubricants in the mixture, caused low dynamic thermal stability, which resulted in browning of the material in the sprue area.

To eliminate the above-mentioned shortcomings, a material for injection molding of shoe sole parts was developed, containing polyvinyl chloride and butadiene acrylonitrile copolymer in a weight ratio of at least 2:1, polyvinyl chloride plasticizers, fillers, lubricants, stabilizers, or blowing agents such as azodicarbonamide, in an amount of from 0.01 to 5% by weight, based on the material, and blowing agent decomposition initiators, the essence of which according to the invention is that it consists by weight of 35 to 60% of a vinyl chloride suspension polymer with a K-value of 55 to 70, plasticized with 25 to 55% diethylhexyl phthalate, 5 to 25% of a linear butadiene acrylonitrile polymer, mixed with 0.25 to 3.0% by weight of an inert filler in the form of silicon dioxide or calcium carbonate, respectively powdered polyvinyl chloride and 2.2 to 13.5% of a stabilizing system with a lubricating effect, facilitating processing on injection molding machines, which stabilizing and lubricating system contains by weight 0.5 to 3.0% of salts of organic fatty acids, in particular oleic, stearic or myristic acids, with combinations of divalent metals Ba-Cd, Ba-Zn, Mg-Zn, Ca-Zn, and Ba-Cd-Zn, 0.5 to 2.0% of alkyl, aryl or alkyl-aryl phosphites, in which the alkyl radical contains 2 to 12 carbon atoms in the chain and the aryl radical is phenyl, 1 to 4% of epoxidized soybean oil, 0.01 to 2% of low molecular weight polyethylene wax and 0.2 to 2.5% of alkyl esters of C1 to C2 fatty acids with a chain length of _C12 to _C22 .

The technical effect of the material according to the invention is that it guarantees safe processability on injection molding machines in the usual range of processing temperatures without unnecessary stress from high thermal and shear forces, so that the temperature course in the chamber of the injection molding device can be sufficiently controlled. This is mainly contributed by the stabilization and lubrication system, the effects of which will be described in more detail in connection with a more detailed description of the individual components of the material according to the invention.

The basis of the material according to the invention is a suspension polymer of polyvinyl chloride with a K-value of 55 to 70, the amount of which is 35 to 60 weight percent, plasticized with diethylhexyl phthalate in an amount of 25 to 55 weight percent. As a modifying component, a linear type of acrylonitrile butadiene polymer is used in an amount of 5 to 25 weight percent, which is characterized by a Mooney ML 4 viscosity in the range of 20 to 55 and the addition of 3 to 12 weight percent, based on the polymer, of a filler inert material, such as powdered polyvinyl chloride, or an inert light-colored filler in the form of CaCO ₃ or SiO ₂ , which improves the mixing of the mixture. This low Mooney ML 4 viscosity value favorably affects the flow properties of the resulting mixture, since it provides a lower melt viscosity. The mixed addition amounts to 0.25 to 3.0 weight percent, calculated on the total material for forming shoe sole parts. As a stabilizing system, a mixture of synergistically acting stabilizer mixtures is used in the material according to the invention. These are 0.5 to 3 weight percent of organometallic salts based on Ba-Cd, or Ba-Zn,

Mg-Zn, Ba-Cd-Zn together with 0.5 to 2 weight percent alkylaryl phosphites and 1 to 4 weight percent epoxidized soybean oil. Such melt properties of the material according to the invention are improved by using 0.2 to 2.5 weight percent effective internal lubricants based on fatty acid esters, which can be combined with up to 2 weight percent highly effective external lubricants based on low molecular weight polyethylene wax. Organometallic salts based on Ba-Cd, Ba-Zn, Mg-Zn or Ca-Zn act as a lubricant with their secondary effect and also contribute to improved melt flow properties. The application of additives in the material according to the invention will guarantee the safe processability of the material in the injection molding technique in the usual range of processing temperatures without the undesirable effects described in the introduction.

The dynamic thermal stability of the mixtures was tested on a Brabender plastograph in the presence of oxygen. It was shown that the use of alkylaryl phosphites has a positive effect on the dynamic thermal stability of the modifying component, i.e. the butadiene acrylonitrile polymer in particular. This ability of alkylaryl phosphites is attributed to their ability to inhibit thermooxidative reactions of polyene segments. Epoxy stabilizers have a positive effect on thermal stability through their ability to deactivate metal chlorides formed by the stabilization reaction and to disperse other stabilizers well. The described lubricant system plays a significant role in the improved flow properties of the material according to the invention. Internal lubricants, such as fatty acid alkyl esters, reduce friction between polymer molecules. External lubricants, such as low molecular weight polyethylene, reduce friction between macromolecules and the tool. Good flow properties were achieved in the material according to the invention, without the risk of migration, by means of a suitable ratio of internal and external lubricants and their optimal dosage. This composition of the mixture allows the use of 0.1 to 2 weight percent of azodicarbonamide-based blowing agents in conjunction with up to 3 weight percent of blowing agent decomposition activators without significantly affecting the dynamic thermal stability. Blowing agent decomposition activators in expanded mixtures, such as zinc stearate or zinc oxide, reduce the decomposition temperature of azodicarbonamide. The cellular structure of the expanded material according to the invention is regular, without large cavities, so-called holes, which are created by tearing the cell walls.

A sufficiently compact layer is created on the surface of the manufactured sole parts, allowing them to be glued to shoe uppers without any problems.

The invention is further explained by several exemplary embodiments, in which the amounts of individual components are given in weight percent.

Example

The sole material is composed of:

PVC polymer suspension K = 65 45.0

Diethylhexyl phthalate

Stabilizer based on Ba-Cd salt of a mixture of stearic acid and oleic acid Dinonylphenylphosphite '

Epoxidized soybean oil Polybutadiene acrylonitrile, ML 4 = 25 Calcium carbonate SiO^-based filler

Stearic acid isooctyl ester Low molecular weight polyethylene with a drop point of 70 to 120 °C

37*0

1.5

1.0

2.2

9.0

1.9

0.9

0.5

1.0

Example 2

For the production of the sole material, a mixture was prepared with the following composition:

PVC polymer suspension K = 70

Diethylhexyl phthalate

Diethylhexyl adipate 9 Stabilizer based on Mg-Zn salt of a mixture of stearic and myristic acids 2.5 Triphenylphosphite 1.5 Epoxidized soybean oil 6.5 Polybutadiene acrylonitrile, ML = ^: 42 . 5.0 Azodicarbonamide 0.5 Zinc oxide 1.0 Stearin 1.0

1) ML 4 is the designation of the physical method for determining Mooney plasticity

Example 3

Composition of the material for preparing the sole:

PVC polymer suspension κ = 60 35.0 Diethylhexyl phthalate 32.0 Stabilizer based on Ca-Zn salt of a mixture of oleic acid and myristic acid 2.0 Trinonyl phosphite 1.5 Epoxidized soybean oil 5.4 Polybutadiene acrylonitrile, ML 4 = 30 20.0 Azodicarbonamide 0.1 Low molecular weight PE 2.0 Stearic acid octyl ester 2.0

All mixtures according to examples 1 to 3 were prepared with a fluid mixing device using the usual procedure for mixing plasticized PVC mixtures. However, polybutadiene acrylonitrile was added only after the mixture had cooled to 50 °C. The dry mixture thus prepared was granulated. Processing on the sole was carried out using the usual procedures in the footwear industry by injection molding on a KUASY machine in examples 1 and 2, and on an Ottogalli machine in example 3. The temperature of the injected melt was 170 to 210 °C. The material according to the invention was tested on a Brabender plastograph.

Attached

For comparison, the technological parameters of the mixture according to Example 1 and according to the following recipe were tested, which represents the standard composition of commonly used modified PVC mixtures in granules; the composition is in weight percent:

PVC/ K = 65 45

Diethylhexyl phthalate 37

Dibutyltin mercaptide 4.7

Polybutadiene acrylonitrile, ML 4 ·= 50 9

Calcium carbonate 2.8

Stearin 1

Calcium stearate 0.5

In terms of processing properties, the following parameters were monitored: dynamic stability, viscosity, plasticity curves and plasticity energy. The values are given in the table:

Parameter Example 1 Standard mix Dynamic stability (min) 30 22 Viscosity 185°C, 60 rpm (Pass) 17 36 Plastic energy/Nm. 180.s ¹ 4.1 ^{- 6'7}

The values given in the table clearly show increased dynamic stability, lower viscosity and lower plasticizing energy, which is the amount of energy required to introduce 75 g of material into the melt in 3 minutes.

The stabilization system shown in the exemplary embodiments represents a dynamic stability value that is optimal from a technical and economic point of view. However, depending on the processing technique used, it is possible to vary the rheological property values within a wide range.

Claims (1)

Injection molding of the shoe sole comprising polyvinyl chloride and butadiene acrylonitrile copolymer in a weight ratio of at least 2: 1, polyvinyl chloride plasticizers, fillers, lubricants, stabilizers or blowing agents such as azodicarbonamide in an amount of from 0.01 to 5% by weight, based on and a blowing agent decomposition initiator comprising 35 to 60% vinyl chloride suspension polymer having a K-value of 55 to 70, softened 25 to 55% diethylhexyl phthalate, 5 to 25 S linear butadiene acrylonitrile polymer blended with 0.25 to 60%. 3.0% by weight of an inert filler in the form of silica or calcium carbonate or powdered polyvinyl chloride and 2.2 to 13.5% of a stabilizing system with lubricating effect, facilitating processing on injection molding machines, the stabilizing and lubricating system containing 0% by weight; 5 up to 3.0% salts of organic fatty acids, especially oleic, stearic or myristic acid, with combinations of divalent metals Ba-Cd, Ba-Zn, Mg-Zn, Ca-Zn and Ba Cd-Zn, 0.5 to 2% alkyl aryl or alkyl aryl phosphites in which the alkyl radical contains 2 to 12 carbon atoms in the chain and the aryl radical is phenyl, 1 to 4% epoxidized soybean oil, 0.01 to 2% low molecular weight polyethylene wax and 0.2 to 2 5% alkyl esters of C ₃ to ^C 10 fatty acids having a chain length of C ₁₂ to C ₂₂ , all percentages being by weight and refer to the material as a whole.