KR101307496B1 - Purging agent for polymer processing - Google Patents

Abstract

PURPOSE: A purging agent for processing a polymer is provided to have an excellent purging effect when inputted into a processing device such as an extruder or an ejector by having a polymer foam shape. CONSTITUTION: A purging agent for processing a polymer includes a polymer foam which has a plurality of foam cells the closed cells ratio of which is 50 % or greater. The polymer foam is formed by foam processing a compound including polyethylene, polypropylene, an ethylene copolymer, a synthetic rubber, a crosslinking agent, and a foaming agent, the density of the polymer foam is 0.1-0.9 g/cc, and the Shore C hardness of the polymer foam is 30-90. When the polymer foam is put into a processing device, the polymer foam is attached to the inner wall and the screw of the processing device.

Description

Purging agent for polymer processing

The technology disclosed herein relates to a purging agent for polymer processing.

Typical molding methods for thermoplastics include injection, extrusion, blow molding, and the like. By the way, if the processing operation is continued with a resin having a specific type and color and then replaced with a resin having a different type or color, the remaining resin may affect subsequent resin products due to the previous resin composition.

Particularly, in the molding and processing of thermoplastic resin products, in which small quantity production of small quantities of various products are changing daily, when changing from colored products to non-colored products or from one colored product to another colored product, cross contamination occurs and the following molded products May cause mixing or surface defects. Therefore, in order to secure the value of the product, the cleaning of the screw, barrel and mold inside the molding machine is an important matter, which involves purging the front resin.

 Generally, the inside of the molding machine is continuously wiped with a resin to be used next time, which uses a purging compound prepared to speed up purging because it takes a long time and a considerable loss of the resin itself. The purging compound is a chemical purging compound using a mechanical purging compound in which an abrasive composed of an inorganic substance such as calcium carbonate is added to the base resin, or a chemical compound mixed with a liquid using a chemical such as ammonia. Alternatively, a chemical / mechanical compound may be formed into pellets by mixing an amine-like drug with an acrylic resin or polyethylene resin.

The use of a double mechanical compound can cause surface damage to screws, cylinders, etc., and the use of a chemical compound can be difficult to handle due to liquids, which can cause problems with the hopper, and the use of chemical / mechanical compounds can lead to high cost and long purging time. The effect may be low.

Therefore, there is a need for more improved purging agents in polymer processing.

According to an aspect of the present invention, there is provided a purging agent for polymer processing, comprising a polymer foam having a plurality of foam cells and comprising at least 50% of the closed cells of the foam cells.

According to another aspect of the invention, the step of obtaining a molded article by extracting from the processing device after molding the first polymer composition into a processing device at a temperature and pressure conditions that can be plasticized or melted; Injecting a purging agent for processing a polymer into the processing machine after the extraction of the first polymer composition; And extracting the first polymer composition remaining on the inner wall or the screw of the processing apparatus together with the polymer processing purging agent to the outside of the processing apparatus as the polymer processing purging agent is processed into the processing apparatus. A purging agent for polymer processing is provided with a purging method including a polymer foam having a plurality of foam cells and containing at least 50% of the closed cells of the foam cells.

Hereinafter, various embodiments of the present invention will be described in more detail.

Purging agent for polymer processing according to an embodiment of the present invention has a plurality of foam cells and has the form of a polymer foam having at least 50% of the closed cells (closed cells) of the foam cells.

The polymer foam is a crosslinked (partially crosslinked or fully crosslinked) low-density polymer that can be compressed by an external force and has the property of restoring its original volume once the external force is removed. Therefore, when cutting the polymer processing purging agent in the form of the polymer foam and forcibly pushed into the processing equipment through the hopper of the processing equipment, the purging agent is compressed and introduced into the processing equipment and then expands again. The expanded polymer foam has a rough surface, which has the effect of scrubbing the surface of a screw or cylinder like a scrubber.

In the polymer foam, the undecomposed blowing agent remaining in the foaming process may remain. Due to the undecomposed foaming agent, the polymer foam is further foamed by the high temperature in the cylinder, and thus the foaming force is more closely adhered to the processing equipment, so that the inner surface of the processing equipment may be more finely wiped.

The polymer foam can be made by foam processing of the polymer. Suitable raw materials for producing the polymer foam by foaming may further include a crosslinking agent, foaming agent, and other additives such as fillers or pigments for foam processing in addition to the basic polymer. The raw materials for preparing the polymer foam are mixed in a kneader such as a kneader or a Banbury mixer, and sheeted or rolled using a roll mill. After crosslinking in the mold of the pressure press at a constant temperature and pressure (for example, a temperature of 150 ~ 250 ℃ and pressure of 100 ~ 300 kg / cm ² ), the mold is opened and foamed or in an injection foaming machine equipped with a mold Specimens in the form of foam (foam, foam) can be obtained by injection molding, crosslinking, and then foaming by opening the mold. Through the shape and subsequent processing of the mold, specimens of hexahedron, cylinder, sphere and various other shapes can be obtained.

The type of polymer used for the polymer foam is not particularly limited as long as it is a foamable resin. The polymer may be a thermoplastic or thermoset material. Suitable polymers used in the polymer foams include polyolefins, polyvinylchlorides, alkenyl aromatic polymers, polycarbonates, polyetherimides, polyamides, polyesters, polyvinylidene chlorides, polymethylmethacrylates, polyurethanes, polyis And isocyanurates, phenols, copolymers and terpolymers thereof, thermoplastic polymer blends and rubber modified polymers. Suitable polyolefins include polyethylene and polypropylene, and ethylene copolymers.

The ethylene copolymer is i) ethylene, ii) C ₃ -C ₁₀ alpha monoolefins, unsaturated C ₃ -C ₂₀ monocarboxylic acid of the C ₁ -C ₁₂ alkyl ester, an unsaturated C ₃ -C ₂₀ mono- or dicarboxylic acids, unsaturated C _It may be a copolymer of at least one ethylenically unsaturated monomer selected from the group consisting of anhydrides of ₄ -C ₈ dicarboxylic acids and vinyl esters of saturated C ₂ -C ₁₈ carboxylic acids.

Specific examples of the ethylene copolymer include ethylene vinyl acetate (Ethylene Vinylacetate, EVA), ethylene butyl acrylate (Ethylene Butylacrylate, BA), ethylene methyl acrylate (Ethylene Methylacrylate, EMA), ethylene ethyl acrylate (Ethylene Ethylacrylate, EEA) ), Ethylene methyl methacrylate (Ethylene Methylmethacrylate, EMMA), ethylene butene copolymer (Ethylene Butene Copolymer, EB-Co), ethylene octene copolymer (Ethylene Octene Coplymer, EO-Co) It may be abnormal.

In one embodiment the polymer used in the polymeric foam contains an alkenyl aromatic polymeric material. Suitable alkenyl aromatic polymeric materials include alkenyl aromatic homopolymers and copolymers of ethylenically unsaturated comonomers copolymerizable with alkenyl aromatic compounds. The alkenyl aromatic polymer material may further contain small amounts of non-alkenyl aromatic polymers. The alkenyl aromatic polymer material may be one or more alkenyl aromatic homopolymers alone, one or more alkenyl aromatic copolymers alone, a combination of one or more alkenyl aromatic homopolymers and copolymers, or a combination of any of the above materials with non-aromatic polymers. It includes.

Suitable alkenyl aromatic polymer materials include those derived from alkenyl aromatic compounds such as styrene, alphamethylstyrene, ethylstyrene, vinylbenzene, vinyltoluene, chlorostyrene and bromostyrene. Small amounts of C2-6 alkyl acids and esters, ionomer derivatives and monoethylenically unsaturated compounds such as C4-6 dienes can be copolymerized with alkenyl aromatic compounds. Examples of copolymerizable compounds include acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, ataconic acid, acrylonitrile, maleic anhydride, methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, methyl Methacrylate, vinyl acetate and butadiene.

In one embodiment, the polymer may be natural or synthetic rubber. The synthetic rubber is styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), nitrile rubber (NBR), chloroprene rubber (CR), chlorosulfonated polyethylene rubber (CSM), ethylene-propylene rubber (EPM ), Ethylene-propylene-diene rubber (EPDM) and the like may be used alone or in combination of two or more.

In one embodiment, the polymer foam may be in a form in which two or more polymers are blended.

Specific examples of the foam include ethylene-vinyl acetate copolymer (EVA) foam, polyethylene (PE) foam, ethylene-propylene-diene terpolymer (EPDM) foam, styrene butadiene rubber (SBR) foam, and the like.

The physical properties of the foam can be modified by the choice of the molecular weight of the polymer. For example, the production of low density foams is facilitated by using low molecular weight polymers, while the production of high density foams can be facilitated by using high molecular weight polymers or high viscosity resins.

Any known most blowing agents (also known as foaming agents or expanding agents) can be used in the raw material composition for making the polymer processing purging agent, including gaseous materials, volatile liquids and chemical agents that decompose into gases and other byproducts. have. The blowing agent is added to prepare a foam, using an azo compound having a decomposition temperature of 150 to 210 ° C, and preferably used in an amount of 0.1 to 6 parts by weight based on 100 parts by weight of the polymer. If the amount used is less than 0.1 part by weight, specific gravity may exceed 0.9 and a hardness of Shore C hardness greater than 90 may be produced, which may cause a problem in purging. Purging can be difficult. And, if the decomposition temperature is less than 150 ℃ early foaming occurs during the compound production, if it exceeds 210 ℃ the molding time of the foam may take 15 minutes or more, productivity may be lowered.

Blowing agents include chemical blowing agents and physical blowing agents, and representative blowing agents include nitrogen, carbon dioxide, air, methyl chloride, ethyl chloride, pentane, isopentane, perfluoromethane, chlorotrifluoromethane, dichlorodifluoromethane, trichloro Fluoromethane, perfluoroethane, 1-chloro-1,1-difluoroethane, chloropentafluoroethane, dichlorotetrafluoroethane, trichlorotrifluoroethane, perfluoropropane, chloroheptafluoropropane , Dichlorohexafluoropropane, perfluorobutane, chlorononafluorobutane, perfluorocyclobutane, azodicarbonamide (ADCA), azodiisobutyronitrile, benzenesulfonhydrazide, 4,4-oxybenzene Sulfonyl-semicarbazide, p-toluene sulfonyl semicarbazide, barium azodicarboxylate, N, N'dimethyl-N, N'-dinitrosoterephthalamide, and Including re-hydrazino-triazine, however, not limited to this. In general, ADCA is the preferred blowing agent.

The crosslinking agent is an organic peroxide crosslinking agent that can sufficiently capture the decomposition gas generated from the blowing agent and impart high temperature viscoelasticity to 0.02 to 4 parts by weight based on 100 parts by weight of the polymer, preferably 0.02 to 3.0 parts by weight, More preferably, 0.05 to 1.5 parts by weight is preferably used, and these are those having a half-life temperature of 130 minutes to 180 ° C. If the amount is less than 0.02 parts by weight, the crosslinking is insufficient, so that the high temperature viscoelasticity of the resin is not maintained when the foam is decomposed. If the content is more than 1.5 parts by weight, the hardness may be sharply increased due to overcrosslinking, and the foam may burst. Examples of such a crosslinking agent include t-butylperoxyisopropyl carbonate, t-butylperoxy urinate, t-butylperoxyacetate, and di-t-butylperoxyphthalate as organic peroxide crosslinking agents commonly used in rubber compounding. , t-dibutyl foroxymaleic acid, cyclohexanone peroxide, t-butyl cumyl peroxide, t-butyl hydroperoxide, t-butyl peroxybenzoate, dicumyl peroxide, 1,3-bis (t-butylper Oxyisopropyl) benzene, methylethylketone peroxide, 2,5-dimethyl-2,5-di (benzoyloxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, di -t-butylperoxide, 2,5-dimethyl-2,5- (t-butylperoxy) -3-hexane, n-butyl-4, 4-bis (t-butylperoxy) valerate, a, a'-bis (t-butylperoxy) diisopropyl benzene etc. can be used.

The other additives are conventional additives used in the manufacture of foams, such as metal oxides, stearic acid, antioxidants, zinc stearate, titanium dioxide, crosslinking aids, etc., which are commonly used in the manufacture of foams to aid processing properties and improve the properties of the foams. In addition, it is also possible to use a variety of pigments in consideration of the color. The additive may be added 4 to 15 parts by weight based on 100 parts by weight of the polymer. As the metal oxide, zinc oxide, titanium oxide, cadmium oxide, magnesium oxide, mercury oxide, tin oxide, lead oxide, calcium oxide, etc. may be used to improve the physical properties of the foam, and may be used in an amount of 1 to 4 parts by weight based on 100 parts by weight of the polymer. Can be. In addition, it is preferable to use 0.05 to 0.5 parts by weight of triaryl cyanurate (TAC), which is a crosslinking aid, based on 100 parts by weight of the polymer to control the molding time to 5 to 10 minutes when the press is 150 to 170 ° C. If the amount of the crosslinking aid is less than 0.05 parts by weight, the crosslinking aid has little effect. If the crosslinking aid exceeds 0.5 parts by weight, the foam may burst due to overcrosslinking, similar to when the amount of the crosslinking agent exceeds 1.5 parts by weight.

Stearic acid and cyan stearate can form foam cells finely and uniformly, facilitate demolding during foam molding, and generally can be used in an amount of 1 to 4 parts by weight based on 100 parts by weight of the substrate. As the antioxidant, sunnoc, butylated hydroxy toluene (BHT), songnox 1076 (songnox 1076, octadecyl 3,5-di-tert-butyl--hydroxy hydrocinnamate) and the like are used. It can be used in an amount of usually 0.25 to 2 parts by weight. Titanium dioxide is used as a pigment for white and functions the same as the aforementioned metal oxide, and may be used in an amount of 2 to 5 parts by weight.

Fillers that can be included in the composition serve to lower the cost of the composition. Examples of the filler include silica (SiO ₂ ), MgCO ₃ , CaCO ₃ , Talc, Al (OH) ₃ , Mg (OH) _2, and the like, and are generally used in an amount of 10 to 50 parts by weight based on 100 parts by weight of the polymer. Can be. The filler may be used as an abrasive to increase the cleaning power of the purging agent.

Purging agent for polymer processing according to an embodiment of the present invention is characterized in that it generally has the following characteristics. The purging agent for polymer processing has a form of a polymer foam and is generally relatively low density, and may be 0.1 to 0.9 g / cc, preferably 0.15 to 0.8 g / cc, and more preferably 0.2 to 0.7 g / cc. If the compression force in the cylinder of the processing machine is less than the above range, the purging effect is weak. If the pressure exceeds the above range, the pressure in the cylinder may be too strong to stop the operation of the injection molding machine.

On the other hand, the purge agent for processing the polymer may have a hardness of a predetermined or more for the effect of the washing power. However, if the hardness is too high, it may be difficult to purge due to too much load on the processing equipment. In general, the suitable hardness range of the purging agent for the polymer processing may have a hardness of Shore C 30 to 90, preferably a hardness of 40 to 90. Low hardness may require a large amount of purging agent due to the reduced cleaning power, and consequently increase the purging time, resulting in decreased productivity.

The resulting polymeric foams generally have a relatively small average bubble (cell) size, typically up to about 3 mm average bubble size. The average bubble size can be measured, for example, in accordance with ASTM D3576-77. In one embodiment, the polymeric foams generally have an average bubble size of about 0.01 mm to about 0.4 mm, but for purging purposes of the present invention, bubble size may be increased to about 3 mm for cleaning effects such as scrubbers.

The resulting polymeric foams can generally have a large amount of closed cells and a small amount of open cells. The relative amount of closed cells can be measured, for example, according to ASTM D2856-A. In one embodiment, at least about 50% of the foam cells of the polymeric foam consist of closed cells. In another embodiment, at least about 70% of the foam cells of the resulting polymeric foam consist of closed cells. In a preferred embodiment, at least about 80% of the foam cells of the resulting polymeric foam are closed cells. In a more preferred embodiment, at least about 95% of the bubbles of the resulting polymeric foam are closed cells. If the closed cells of the foam cells in the polymer foam is 50% or more may have a compression force suitable for the purging agent.

If a polymer foam having a foam cell having a mostly open cell structure, such as polyurethane foam, urea foam, latex foam as a polymer processing purging agent, the air inside the foam cell may escape as pressed. Therefore, when the polymer foam is added as a purging agent in the processing equipment, the tightness may be less, and the washing effect may be reduced.

Examples of suitable polymeric foams for use in the purging agent for polymer processing according to one embodiment of the present invention include at least one polymer, crosslinking agent and blowing agent selected from the group consisting of polyethylene, ethylene-vinylacetate copolymer, polyolefin elastomer, EPDM and SBR It may be formed by foaming a compound comprising a.

According to one embodiment of the present invention there is provided a purging method using the above-mentioned purging agent for polymer processing.

First, the first polymer composition is molded into a processing device at a temperature and pressure condition capable of plasticizing or melting, and then extracted from the processing device to obtain a molded product. Next, after the extraction of the first polymer composition, a purge agent for processing the polymer is added to the processing device. Subsequently, the first polymer composition remaining on the inner wall or the screw of the processing device is extracted together with the polymer processing purging agent to the outside of the processing device as the polymer processing purging agent is processed into the processing device. In this case, the purging agent for polymer processing includes a plurality of foaming cells and contains at least 50% of the closed cells. Thereafter, if necessary, the first polymer composition and the second polymer composition, which are different from each other, are introduced into the processing machine to prepare a new molded article. By using a purge agent in the form of a polymeric foam, it is possible to reduce the amount of purge agent and shorten the purging time due to the excellent cleaning effect.

Although various foams are effective as the purging agent for the polymer processing, there are differences in the degree of effect depending on the type of foam material, foam cell structure, density, hardness, foam particle size, and the like.

For example, the polymer foam material may be more excellent in the purging effect when using a material having excellent elasticity, the same as the first polymer composition or good miscibility. As mentioned above, the foamed cell structure is also advantageous as more closed cells are than open cells. Although the foam particle size also varies depending on the processing equipment, it is easy to handle a particle shape having a size of a size that can be introduced into the processing equipment. If the foam particles are too large, they are difficult to enter into the valley of the screw.

On the other hand, as described above, if the density or hardness of the specimen is too high, it may be difficult to stop due to a large load on the processing equipment. On the other hand, if the density or hardness is too low, the purging time may be too long.

As described above, the purging agent for polymer processing according to one embodiment of the present invention has a form of a polymer foam, and thus, when it is introduced into a processing equipment such as an extruder or an injection molding machine, the purging effect is excellent in washing against the inner wall of the processing equipment and screws. .

Hereinafter, the present invention will be described with reference to more specific examples, but the spirit of the present invention is not limited thereto.

[Example]

Example  One

100 parts by weight of EVA (VA 15%, MI 2.5), 1.0 part by weight of stearic acid, 5.0 parts by weight of zinc oxide, 10.0 parts by weight of CaCO ₃ , 1.0 parts by weight of DCP, 2.0 parts by weight of ADCA, TiO ₂ After mixing 5.0 parts by weight in a kneader and sheeting in a 2 roll mill, put it in a mold of a press press heated to 150 ° C (200 mm x 200 mm x 20 mm) and crosslink for 20 minutes. The mold was opened and foamed to obtain a foam specimen of 300 mm x 300 mm x 30 mm size. The hardness was Shore C 60 and the density was 0.20 g / cc. Skiving this and cutting with a wire cutter to obtain a cube having a side length of 10mm, 20mm, 30mm to call Examples 1-1, 1-2, 1-3. In the present specification, MI was measured at 190 ° C. × 2.16 kg and the unit is g / 10 min.

Comparative example  3

100 parts by weight of EVA (VA 28%, MI 2.5), 1.0 part by weight of stearic acid, 5.0 parts by weight of zinc oxide, 10.0 parts by weight of CaCO ₃ , 1.0 part by weight of dicumyl peroxide (DCP), ADCA 4.0 Parts by weight, 5.0 parts by weight of TiO ₂ are mixed in a kneader, sheeted in a 2 roll mill, and then placed in a mold of a press press heated to 150 ° C. (Cavity: 200 mm x 200 mm x 20 mm). After crosslinking for 20 minutes, the mold was opened and foamed to obtain a foam specimen having a size of 400 mm x 400 x 40 mm. The hardness was Shore C 20 and the density was 0.08 g / cc. This was skived and cut with a wire cutter to obtain cubes having lengths of 10 mm, 20 mm, and 30 mm in length, and were referred to as Comparative Examples 3-1, 3-2, and 3-3, respectively.

Example  2

100 parts by weight of EVA (VA 15%, MI 2.5), 1.0 part by weight of stearic acid, 5.0 parts by weight of zinc oxide, 10.0 parts by weight of CaCO ₃ , 1.0 parts by weight of DCP, 2.0 parts by weight of ADCA, TiO ₂ 5.0 parts by weight were mixed in a kneader and sheeted in a 2 roll mill, then injected from an injection foaming machine equipped with a mold heated to 170 ° C. (a sphere having a diameter of 14 mm). After crosslinking for 20 minutes, the mold was opened and foamed to obtain a large number of spherical foam specimens having a diameter of 20 mm. The hardness was Shore C 60 and the density was 0.20 g / cc.

Example  3

100 parts by weight of polyolefin elastomer (density 0.88 g / cc, MI 3.0), 1.0 part by weight of stearic acid, 5.0 parts by weight of zinc oxide, CaCO ₃ 10.0 parts by weight, DCP 1.0 parts by weight, ADCA After mixing 2.0 parts by weight, 5.0 parts by weight of TiO _{2 in a} kneader and sheeting in a 2 roll mill, a mold of a pressurized press heated to 150 ° C. (Cavity: 200 mm x 200 mm x 20 mm) After crosslinking for 20 minutes, the mold was opened and foamed to obtain a foam specimen having a size of 300 mm x 300 mm x 30 mm. The hardness was Shore C 60 and the density was 0.18 g / cc. Skiving this and cutting with a wire cutter cut to 20mm length.

Example  4

100 parts by weight of EPDM rubber, 1.0 part by weight of stearic acid, 5.0 parts by weight of zinc oxide, 10.0 parts by weight of CaCO ₃ , 1.0 parts by weight of DCP, 2.0 parts by weight of ADCA, and 5.0 parts by weight of TiO ₂ . After mixing in the 2 roll mill (sheeting), and placed in a mold (Cavity: 200mm x 200mm x 20mm) of pressurized press heated to 150 ℃, crosslinked for 20 minutes, open the mold and foamed to 260mm x 260 mm x 27 mm sized foam specimens were obtained. The hardness was Shore C 40 and the density was 0.30 g / cc. Skiving this and cutting with a wire cutter cut to 20mm length.

Example  5

100 parts by weight of EVA (VA 15%, MI 2.0), 1.0 part by weight of stearic acid, 5.0 parts by weight of zinc oxide, 10.0 parts by weight of CaCO ₃ , 1.0 parts by weight of DCP, 2.0 parts by weight of ADCA, TiO ₂ After mixing 5.0 parts by weight in a kneader and sheeting in a 2 roll mill, put into a mold of a press press heated to 150 ° C (Cavity: 200mm x 200mm x 20mm) and crosslink for 20 minutes. The mold was opened and foamed to obtain a foam specimen of 240 mm x 240 mm x 24 mm size. The hardness was Shore C 88 and the density was 0.45 g / cc. Skiving this and cutting with a wire cutter cut to 20mm length.

Example  6

100 parts by weight of EVA (VA 33%, MI 2.0), 1.0 part by weight of stearic acid, 5.0 parts by weight of zinc oxide, 10.0 parts by weight of CaCO ₃ , 1.0 parts by weight of DCP, 0.6 parts by weight of ADCA, TiO ₂ After mixing 5.0 parts by weight in a kneader and sheeting in a 2 roll mill, put it in a mold of a press press heated to 150 ° C (200 mm x 200 mm x 20 mm) and crosslink for 20 minutes. The mold was opened and foamed to obtain a foam specimen of 230 mm x 230 mm x 23 mm size. The hardness was Shore C 57 and the density was 0.70 g / cc. Skiving this and cutting with a wire cutter cut to 20mm length.

Comparative example  4

100 parts by weight of EVA (VA 45%, MI 2.0), 1.0 part by weight of stearic acid, 5.0 parts by weight of zinc oxide, 10.0 parts by weight of CaCO ₃ , 1.0 parts by weight of DCP, 0.3 parts by weight of ADCA, TiO ₂ After mixing 5.0 parts by weight in a kneader and sheeting in a 2 roll mill, put it in a mold of a press press heated to 150 ° C (200 mm x 200 mm x 20 mm) and crosslink for 20 minutes. The mold was opened and foamed to obtain a foam specimen of size 206 mm x 206 mm x 21 mm. The hardness was Shore C 55 and the density was 0.92 g / cc. Skiving this and cutting with a wire cutter cut to 20mm length.

Comparative example  5

50 parts by weight of EVA (VA 6%, MI 2.0), 50 parts by weight of LDPE (density 0.92 g / cc, MI 3.0), 1.0 part by weight of stearic acid, 5.0 parts by weight of zinc oxide, CaCO ₃ 10.0 Parts by weight, DCP 1.0 parts by weight, ADCA 1.0 parts by weight, TiO ₂ 5.0 parts by weight in a kneader and sheeting in a 2 roll mill, and then press mold of a press Cavity: 200mm x 200mm x 20mm) was crosslinked for 20 minutes, and the mold was opened and foamed to obtain a foam specimen of 240mm x 240mm x 24mm size. The hardness was Shore C 95 and the density was 0.45 g / cc. Skiving this and cutting with a wire cutter cut to 20mm length.

<Purging test>

* Test Material 1: Polypropylene

Comparative example  1-1

Polypropylene (homopolymer, density 0.90 g / cc, MI 14.0, PP-) colored in red with a mold with a cavity of 400 cc in an injection molding machine with a screw diameter of 50 mm, a screw L / D 18: 1 and a clamping force of 150 tons Extruded for 10 minutes and then replace the color with polypropylene (homopolymer, density 0.90g / cc, MI 14.0, PP-B) colored white, red with PP-B It took 30 minutes to disappear and completely replaced with white to get the PP-B injection pass, and the amount of PP-B consumed for purging was 25 kg.

Comparative example  2-1

Polypropylene colored with red color after mounting a mold with a Cavity 400CC in an injection molding machine with a screw diameter of 50 mm, a screw L / D 18: 1 and a clamping force of 150 tons (homopolymer, density 0.90 g / cc, MI 14.0, PP-A) After 10 minutes of injection, the color is changed to white colored polypropylene (homopolymer, density 0.90g / cc, MI 14.0, PP-B) and ASACLEAN UP (purging compound made by Asahi Kasei) Wipe until white disappears, and wipe until PP-B disappears, and it takes 8 minutes until PP-B injection passes.The amount of ASACLEAN UP spent on purging was 1.0 kg and the amount of PP-B was 2.0 kg.

Example  1 to 6 and Comparative example  3 to 5

After inserting a mold of Cavity 400cc into an injection molding machine with a screw diameter of 50mm, a screw L / D 18: 1 and a clamping force of 150 tons, and injecting PP-A for 10 minutes, the specimens of Examples 1-6 and Comparative Examples 3-5 were Each was put in an injection molding machine hopper and purged, and then purged with PP-B until the acceptance product came out.

[Table 1]

Part-1: Particles in the foam are too large to enter the screw. Must be forced by hand

Part-2: Too much load on the screw stops the purging operation.

From the result of Table 1, the purging time was shortened when using the comparative purging agent 2-1 using the commercial purging agent or the foam purging agent which concerns on this invention (Example 1-1, 1-). 2, 2 to 6). In the case of using the purging agent in the form of foam according to the present invention, it has been shown to have a purging effect equal to or greater than that of using a commercial purging agent (ASACLEAN UP). In the case of Examples 1-1, 1-2, 2, and 3, the required amount of purging agent was smaller than that of Comparative Example 2-2 while having the same purging time and PP-B requirement, and in Examples 5 and 6, Comparative Example 2-2 Purging times were shorter and PP-B requirements were smaller.

On the other hand, the foam purging agent is compressible, but in order to be applied to a processing machine, the particle size needs to be adjusted within a certain size (see Example 1-3). In addition, if the hardness or density is too low, as in Comparative Examples 3-1 to 3-3, the purging time may be greatly increased due to the decrease in washing power. On the contrary, if the hardness or density is too high as in Comparative Examples 4 and 5, the purging operation may be difficult. Can be.

* Test Material 2: Nylon 6

Comparative example  1-2

The injection molding machine with a screw diameter of 50mm, screw L / D 18: 1, and a clamping force of 150 tons was mounted with a 300cc cavity mold and then colored with nylon 6 (density 1.14g / cc, Mp 255 ℃, hardness R120, PA-A). After 10 minutes of injection, the color is changed to white colored nylon 6 (density 1.14g / cc, Mp 255 ℃, hardness R120, PA-B). It took 40 minutes until it disappeared and completely replaced with white, and the PA-B injection passed, and the amount of PA-B consumed for purging was 38 kg.

Comparative example  2-2

The injection molding machine with a screw diameter of 50mm, screw L / D 18: 1 and a clamping force of 150 tons was mounted in a mold with a cavity of 300cc and then colored with nylon 6 (density 1.14g / cc, Mp 255 ℃, hardness R120, PA-A). After 10 minutes of injection, the color is changed to white colored nylon 6 (density 1.14g / cc, Mp 255 ° C, hardness R120, PA-B), and ASACLEAN U (manufactured by Asahi Kasei) Wipe with a purging compound until white disappears and wipe with PA-B until ASACLEAN U disappears. It took 10 minutes to get the PA-B injection pass, the amount of ASACLEAN U consumed for purging was 1.2 kg and PA- The amount of B was 2.5 kg.

Example  1 to 6 and Comparative example  3 to 5

After inserting a mold with a cavity of 300cc into a injection molding machine with a screw diameter of 50mm, a screw L / D 18: 1 and a clamping force of 150 tons, and injecting PA-A for 10 minutes, the specimens of Examples 1 to 6 and Comparative Examples 3 to 5 were prepared. Each was put in an injection molding machine hopper and purged, and then purged with PA-B until the acceptance product came out.

[Table 2]

Part-1: Particles in the foam are too large to enter the screw. Must be pushed by hand

Part-2: Too much load on the screw stops the purging operation.

From the result of Table 2, the purging time was shortened when using the comparative purging agent 2-2 using the commercial purging agent or the foam purging agent which concerns on this invention compared with the comparative example 1-2 (Example 1-1, 1- 2, 2 to 6). It has been shown that the use of a purging agent in the form of a foam according to the invention generally has a purging effect equal to or greater than that of a commercial purging agent (ASACLEAN U). In the case of Examples 1-1, 1-2, 2, and 3, the required amount of purging agent was smaller than that of Comparative Example 2-2 while having the same purging time and PA-B requirements, and in Examples 5 and 6, Comparative Example 2-2 Purging times were shorter and PA-B requirements were smaller.

On the other hand, the foam purging agent is compressible, but in order to be applied to a processing machine, the particle size needs to be adjusted within a certain size (see Example 1-3). In addition, if the hardness or density is too low, as in Comparative Examples 3-1 to 3-3, the purging time may be greatly increased due to the decrease in washing power. On the contrary, if the hardness or density is too high as in Comparative Examples 4 and 5, the purging operation may be difficult. Can be.

Claims (5)

It includes a polymer foam having a plurality of foam cells and wherein the closed cells (closed cells) of more than 50%,
The polymer foam is formed by foaming a compound comprising polyethylene, polypropylene, an ethylene copolymer or a synthetic rubber polymer, a crosslinking agent and a blowing agent, and has a density of 0.1 to 0.9 g / cc and a Shore C hardness of 30 to 90. A purge agent for polymer processing, which is a cross-linked polymer in the form of foam and is in close contact with the inner wall and the screw of the processing machine when the polymer foam is introduced into the processing machine. delete delete delete delete