JP6909394B2 - Foam auxiliary material and foam molding method - Google Patents

Description

The present invention relates to a foaming auxiliary material used in foam molding, and further relates to a foam molding method.

As foam molded products, for example, various air conditioning ducts installed in an instrument panel of an automobile are known. Foam ducts formed by molding a foamed resin material are widely used for these air conditioning ducts. The foam duct is lightweight and can be easily manufactured by adding a foaming agent to a resin material such as a polyolefin resin, melt-kneading the duct, and blow-molding the foamed parison extruded from the die of the extruder.

As a resin material used for foam blow molded products, polyolefin-based resins are widely used, and polypropylene-based resins are particularly common. In recent years, replacement with a polyethylene-based resin has been studied for the purpose of making the material composition cheaper (see Patent Document 1 and the like).

Patent Document 1 describes high-density polyethylene having a long-chain branched structure, a specific gravity of 0.95 to 0.96, a melt flow rate (MFR) of 3 to 7 g / 10 minutes, and a melt tension of 100 to 250 mN, and a melt flow rate. A blow-molded automobile duct is disclosed by adding a chemical foaming agent to a mixed resin in which (MFR) 0.3 to 1.0 g / 10 minutes of high-density polyethylene is mixed.

Japanese Unexamined Patent Publication No. 2011-194700

By the way, in foam molding for molding an effervescent molded product, it is preferable to blend a nucleating agent for forming foam nuclei and a dispersant for dispersing the nucleating agent with the raw material resin. Further, when the used resin is used for recycling, it is preferable to blend the raw material resin with an antioxidant or the like that suppresses resin deterioration. For example, by blending a chemical foaming agent or inorganic particles with a raw material resin as a so-called nucleating agent, the diameter of bubbles becomes smaller. Reducing the diameter of bubbles contributes to the improvement of bubble density, and contributes to the improvement of heat insulation and impact resistance of the product.

Therefore, in foam molding, it is widely practiced to blend chemical foaming agents, inorganic particles, dispersants, etc. into the raw material resin, but in general, the raw material resin is obtained by pelletizing these materials individually. It is mixed with pellets. Specifically, pellets containing inorganic particles, pellets containing a chemical foaming agent, and pellets containing a dispersant are prepared in advance, and these are mixed with the raw material resin pellets according to the blending amount of each component, and in the cylinder. Knead.

However, when each component is pelletized separately and mixed with the raw material resin pellet in this way, the amount of the nucleating agent and the dispersant added is small with respect to the raw material resin, so that the amount is likely to vary and uneven. There is a problem. In addition, although each component exerts its function when it comes into contact with each other, if it is added in pellets separately, the probability of contact with each other decreases, and there is a possibility that it will not function sufficiently. For example, if the dispersant does not come into sufficient contact with the inorganic powder or the chemical foaming agent, the dispersion becomes insufficient, the diameter of the bubbles cannot be sufficiently reduced, or foreign matter adheres to the peripheral portion of the die head or the like. Can be a problem. If foreign matter adheres to the device, it may be mixed into the product, which causes deterioration of the quality of the product.

The present invention has been proposed in view of such conventional circumstances, and can sufficiently exert the functions of a nucleating agent, a dispersant, etc., sufficiently reduce the diameter of bubbles, and provide an apparatus. It is an object of the present invention to provide a foaming auxiliary material capable of preventing foreign matter from adhering to the product and mixing of foreign matter into the product, and further to provide a foam molding method.

In order to achieve the above-mentioned object, the foaming aid of the present invention is kneaded together with a raw material resin pellet made of a polyolefin resin, and is used for foam molding for molding a foamed resin using a physical foaming agent. It is a material, and is characterized in that inorganic particles, a chemical foaming agent, and a dispersant are added to the diluted resin, and the diluted resin is LLDPE .

By adding the inorganic particles that function as a nucleating agent and the chemical foaming agent and the dispersant to the same pellet in advance, the probability of contact with each other increases when kneading with the raw material resin pellets, and the function of each component becomes higher. It is fully demonstrated. In addition, the dispersibility of the nucleating agent in the raw material resin is also good, and variations in the amount and occurrence of unevenness can be suppressed.

On the other hand, the foam molding method of the present invention is a foam molding method for foam molding a resin material, in which inorganic particles, a chemical foaming agent, and a dispersant are simultaneously added to the raw material resin in a state of being mixed in advance. It is a feature.

In the foam molding method of the present invention, the nucleating agent and the dispersant are simultaneously added to the raw material resin in a mixed state. For example, like the foaming aid of the present invention, a pellet containing an inorganic particle that functions as a nucleating agent, a chemical foaming agent, and a dispersant is mixed with a raw material resin as a master batch. As a result, the probability that each component comes into contact with each other increases, and the function of each component is fully exhibited. In addition, the dispersibility of the nucleating agent in the raw material resin is also good, and variations in the amount and occurrence of unevenness can be suppressed.

According to the present invention, it is possible to fully exert the functions of a nucleating agent, a dispersant, etc. to reduce the diameter of bubbles and prevent foreign substances from being mixed, and it is possible to manufacture a high-quality foam molded product. Is. Further, according to the present invention, it is possible to suppress variations in the amount of additive components such as nucleating agents and dispersants, and it is possible to provide foamed molded products having no variation in quality.

It is a schematic perspective view which shows an example of a foam duct. It is the schematic cross-sectional view which shows typically the mode at the time of blow molding a duct.

Hereinafter, embodiments of the foam auxiliary material and the foam molding method to which the present invention is applied will be described in detail with reference to the drawings, taking the production of a foam duct as an example.

The foam duct 10, which is a foam blow molded product, is configured so that air conditioning air supplied from an air conditioner unit (not shown) is circulated through an internal flow path and is ventilated to a desired portion. The shape of the foam duct 10 is not limited to that shown in FIG. 1, and may be any shape depending on the application, installation location, and the like.

The foam duct 10 is obtained by sandwiching a foam parison formed by extruding a foam resin from a die of an extruder with a mold and blow molding. The duct immediately after blow molding is in a state where both ends are closed, and both ends are cut by trimming after blow molding to form an opening shape.

The foam duct 10 is made of a hollow foam resin molded product whose tube wall is composed of a foam layer. By adopting a structure in which the foam layer has a closed cell structure, a duct that is lightweight and has excellent heat insulating properties can be obtained. The closed cell structure is a structure having a plurality of independent cell cells, and means a structure having a closed cell ratio of at least 70% or more. With such a configuration, even when the cooling air is circulated in the foam duct 10, the possibility of dew condensation can be almost eliminated.

In the production of a foam molded product such as the foam duct 10, a required additive is added to the raw material resin and subjected to blow molding. In blow molding, a foamed resin is molded using a physical foaming agent. As the physical foaming agent, an inorganic foaming agent such as air, carbon dioxide, nitrogen gas, or water, or an organic foaming agent such as butane, pentane, hexane, dichloromethane, or dichloroethane can be used. Among these, it is preferable to use air, carbon dioxide gas, or nitrogen gas as the foaming agent. By using these, it is possible to prevent the mixing of organic substances and suppress the deterioration of durability and the like.

Moreover, it is preferable to use a supercritical fluid as a foaming method. That is, it is preferable to put carbon dioxide gas or nitrogen gas in a supercritical state and foam the raw material resin. By using a supercritical fluid, foaming can be performed uniformly and reliably. The conditions when the supercritical fluid is nitrogen gas may be, for example, a critical temperature of 149.1 ° C. and a critical pressure of 3.4 MPa, and the conditions when the supercritical fluid is carbon dioxide gas are, for example, a critical temperature. The temperature may be 31 ° C. and the critical pressure may be 7.4 MPa.

The foam duct 10 is formed by blow molding the raw material resin thus foamed by a known method. FIG. 2 is a diagram showing an aspect of blow molding the foam duct 10.

In blow molding, first, the raw material resin used for molding is kneaded in the extruder to prepare a base resin. Any resin can be used as the raw material resin, but the effect of the present invention is great when a polyolefin-based resin, particularly a polyethylene-based resin, is used.

As the polyethylene-based resin, low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear short-chain branched polyethylene (LLDPE) and the like can be used. Further, it may be a copolymer of ethylene and another copolymerizable monomer. In either case, it is preferable to contain polyethylene having a long-chain branched structure. By using polyethylene having a long-chain branched structure, foamability becomes good.

Polyethylene having a long-chain branched structure (hereinafter, referred to as long-chain branched polyethylene) is as described in, for example, Japanese Patent Application Laid-Open No. 2012-136598, and has a branched structure only at the end of the long-chain polyethylene chain. It has a feature that the number of branched structures is smaller than that of general polyethylene.

The long-chain branched polyethylene can be produced by carrying out ethylene polymerization using a catalyst composed of an organically modified clay mineral obtained by modifying a clay mineral belonging to the smectite group hectorite with a specific organic compound and an organoaluminum compound. ..

The physical properties of the long-chain branched polyethylene used are arbitrary, but for example, the density is preferably in the range of 925 to 970 kg / m3, particularly preferably 930 to 960 kg / m3, as a value of the density measured in accordance with JIS K7676. It is in the range of m3. Further, the long-chain branched polyethylene used preferably shows two peaks in the molecular weight measurement by GPC.

Further, the ratio of the weight average molecular weight (Mw) to the number average molecular weight Mn (Mw / Mn) of the long-chain branched polyethylene used is 2.0 to 7.0, preferably 2.5 to 7.0, and more preferably. It is 3.0 to 6.0. The number average molecular weight (Mn) measured by GPC is preferably 15,000 or more, more preferably 15,000 to 100,000, and particularly preferably 15,000 to 50,000.

The preferred number of long-chain branched polyethylenes used is 0.02 or more per 1000 carbon atoms in the main chain. The number of long-chain branches of a fraction having Mn of 100,000 or more obtained by molecular weight separation is 0.15 or more per 1000 carbon atoms of the main chain. It is desirable that the proportion of fractions having a number average molecular weight of Mn of 100,000 or more obtained by molecular weight fractionation is less than 40% of the total polymer.

The raw material resin (for example, polyethylene-based resin) is generally pelletized and used. The raw material resin pellets are charged from the hopper of a blow molding machine and melt-kneaded in a cylinder. At this time, the necessary additives are added at the same time and kneaded with the raw material resin. Additives include dispersants, inorganic particles that function as nucleating agents, and chemical foaming agents.

The inorganic particles and the chemical foaming agent are used to form foam nuclei in the raw material resin, and function as a nucleating agent. Examples of the inorganic particles include talc and calcium carbonate, but talc is preferable because of its large effect and the improvement of rigidity. As the chemical foaming agent, an inorganic foaming agent such as sodium hydrogen carbonate (baking soda), which is tasteless and odorless and has a non-toxic decomposition residue, is suitable. Citric acid, citrate, etc. can also be used in combination as the chemical foaming agent. In this case, for example, baking soda or the like is added as a main chemical foaming agent, citric acid or the like is added as an auxiliary chemical foaming agent.

The dispersant is used to evenly disperse the inorganic particles and the chemical foaming agent in the raw material resin, and metal soap and the like are used. The metal soap is a metal salt other than the long-chain fatty acids sodium and potassium, and examples thereof include stearic acid soap, hydroxystearic acid soap, lauric acid soap, and behenic acid soap.

The usual method is to pellet these inorganic particles, chemical foaming agents, and dispersants individually, add them to the raw material resin pellets, and mix them. However, in the present embodiment, pellets containing all of these components (foaming aid). Material) is prepared, mixed with raw material resin pellets as a master batch, and melt-kneaded.

The pellets (foaming aid) used as a master batch are made by adding the inorganic particles, a chemical foaming agent, and a dispersant to a diluted resin and pelletizing them. Inorganic particles, a chemical foaming agent, and a chemical foaming agent are added to one pellet. It contains a dispersant. Although any resin can be used as the diluted resin, it is preferable to use a resin having a melting point lower than that of the raw material resin. For example, when the raw material resin is high-density polyethylene or long-chain branched polyethylene, high MFR low melting point LLDPE for injection or the like is used.

In foam molding, the above-mentioned masterbatch is blended with the raw material resin pellets in a predetermined amount, kneaded in the cylinder of the extruder, stored in an accumulator (not shown) in the die, and then stored in an accumulator (not shown). After the predetermined amount of resin is stored, the ring-shaped piston (not shown) is pushed down in the direction orthogonal to the horizontal direction (vertical direction). Then, it is extruded from the die slit of the annular die 21 shown in FIG. 2 as a cylindrical parison P at an extrusion speed of 700 kg / hour or more between the divided dies 31 and 32 constituting the mold clamping device 30. After that, the split dies 31 and 32 are molded to sandwich the parison P, and air is further blown into the parison P in a pressure range of 0.05 to 0.15 MPa to form a foam duct 10.

The method for molding the foam duct 10 is not limited to blow molding as described above, and vacuum molding may be used in which the extruded parison is sucked into a mold to form a molded product having a predetermined shape. Further, compression molding may be used in which the extruded parison is sandwiched between molds without blowing or sucking air.

Further, when molding the foam duct 10, a mixed resin obtained by mixing a recovered resin material and an unused resin (virgin resin) may be used as a raw material resin, and a foaming agent or the like may be added to the raw material resin for foam blow molding. It is possible.

When a resin molded product is molded by general blow molding, the molten resin material is shaped into the shape of the mold surface, and then released from the mold in a cooled and solidified state, and burrs around the molded product, etc. A finished product is obtained by cutting the opening and the opening with a cutter or the like. In the manufacturing cycle for mass production by blow molding, from the viewpoint of resource saving and cost reduction, the recovered resin obtained by crushing the parts other than the finished product in the resin material once melted and then solidified. Use as a material. Then, the recovered resin material is mixed with a virgin resin to which no heat history has been added to obtain a mixed resin, and a foaming agent or the like is added to perform blow molding again.

In the production cycle in such mass production, the ratio of the recovered resin material to the resin material used for molding may be as high as 70 to 90% in some cases. For example, after blow molding, about 10 to 30% of the virgin resin obtained by taking out the finished foam molded product is added to the recovered resin material by the blow molding to add about 10 to 30% to the mixed resin. When blow molding is performed again, the proportion of the recovered resin material is 70 to 90%.

When the manufacturing cycle of performing blow molding in this way, adding virgin resin to the recovered resin material by the blow molding to make a mixed resin, and performing blow molding again is repeated, a foam molded product by molding using the mixed resin. The properties of (foam duct 10) are often deteriorated as compared with the properties of a foam molded product obtained by molding using only virgin resin.

In particular, when a polyethylene-based resin is used as the resin material of the foam duct 10, as described above, polyethylene is oxidatively deteriorated due to repeated heat history to generate crosslinked products, and the crosslinked products of the crosslinked polyethylene are generated during blow molding. Is the core, and there is a big problem that pinhole defects occur from this point. In particular, when a foam duct having a foaming ratio (a value obtained by dividing the density of the resin by the apparent density including air bubbles) is 1.5 times or more is formed, the occurrence of defects becomes remarkable.

In such a case, it is preferable to add an antioxidant to the raw material resin. At this time, the amount of the antioxidant added must be set so that the total content of the antioxidant in the polyethylene resin (foam molded product) is 300 ppm or more, and the total content is 500 ppm or more. It is preferable to add it. If the total content of the antioxidant is less than 300 ppm, the effect may be insufficient, and it becomes difficult to suppress cross-linking deterioration for a long period of time.

As the antioxidant, any known one can be used, and various antioxidants can be used alone or in combination. In particular, it is effective to use a specific antioxidant (phenolic antioxidant and phosphorus-based antioxidant) in combination.

As the antioxidant, there are an antioxidant having a function of capturing radicals (first antioxidant) and an antioxidant that decomposes peroxide (second antioxidant), and the former (second antioxidant). As the antioxidant (1), a phenol-based antioxidant, a hindered amine-based compound (HALS-based), and the like are known. Examples of the latter (second antioxidant) include phosphorus-based antioxidants and sulfur-based antioxidants. In resins, radicals are generated by heat, light, and shear, but if the generated radicals are left unattended, crosslink deterioration and oxidative deterioration occur, and the physical properties deteriorate. The former [antioxidant having an action of capturing radicals (first antioxidant)] has an action of catching generated radicals, and thereby has a function of preventing crosslink deterioration and oxidative deterioration. On the other hand, the latter [antioxidant that decomposes peroxide (second antioxidant)] has the function of decomposing peroxides (radicals) generated by thermal oxidation into alcohol and stopping the chain deterioration reaction. Have.

However, for example, when only an antioxidant that decomposes peroxide (second antioxidant) is added, when a recycling test with a heat history is performed, the melt tension MT increases significantly after the heat history and oxidation occurs. It was found that the preventive effect tends to be insufficient. The parameter observed when oxidatively deteriorated is that the melt tension MT is large, and pinholes occur during molding due to oxidatively deteriorated foreign matter.

On the other hand, when only an antioxidant having a function of capturing radicals (first antioxidant) is added, a recycling test in which a heat history is added shows an effect that the melt tension MT decreases after the heat history. It was found that the addition of a large amount of 500 ppm or more caused a decrease in the melt tension MT, which was a problem. When the melt tension MT becomes small, the parison does not follow when the blow ratio is high in blow molding, and pinholes are likely to occur.

On the other hand, by combining the first antioxidant and the second antioxidant, a sufficient antioxidant effect is exhibited, and the melt tension observed when only the first antioxidant is added. The decrease in MT can be offset by the addition of a second antioxidant, and the amount of change in melt tension MT can be minimized.

Here, the first antioxidant may be any of the above-mentioned phenol-based antioxidants, hindered amine-based compounds (HALS-based), and the like, but among them, phenol-based antioxidants are preferable. The second antioxidant may be any of a phosphorus-based antioxidant, a sulfur-based antioxidant, and the like, but a phosphorylated antioxidant is preferable. Phenol-based antioxidants and phosphorus-based antioxidants are easily available, can be stably supplied, and have high purity, and are excellent in practicality. In addition, phosphorus-based antioxidants are also characterized by being excellent in hydrolysis resistance and volatilization resistance. Phenolic antioxidants are antioxidants that are effective in improving the heat resistance of various resins and elastomers, and have the characteristics of low extractability and low volatilization due to their high molecular weight.

As mentioned above, by using a phosphorus-based antioxidant and a phenol-based antioxidant in combination, a synergistic effect is exhibited, cross-linking deterioration and oxidative deterioration of the polyethylene-based resin are effectively suppressed, and at the time of recycling. Changes in melt tension MT and the like can also be suppressed.

As the phosphorus-based antioxidant and the phenol-based antioxidant, any known one can be used. For example, phosphorus-based antioxidants include high-molecular-weight phosphorus-based antioxidants and low-molecular-weight phosphorus-based antioxidants, either of which may be used, or a mixture of these may be used.

Specific compounds include tris (2,4-branched C3-8 alkyl-butylphenyl) phosphite [tris (2,4-di-t-butylphenyl) phosphite, as an example of a high molecular weight phosphorus antioxidant. Etc.] and tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylene phosphite and the like (2,4-di-branched C3-8 alkylphenyl) -4,4'-C2 -4 alkylene phosphite and the like can be mentioned. Commercially available products include those manufactured by Ciba Japan Co., Ltd. and having a trade name of "Irgafos 168".

Low molecular weight phosphorus antioxidants include triphenylphosphine, diphenylisodecylphosphine, phenyldiisodecylphosphine, tris (nonylphenyl) phosphine; tri-2,4-dimethylphenylphosphine, tri-2,4. Examples of phosphine compounds such as 6-trimethylphenylphosphine, tri-o-tolylphosphine, tri-m-tolylphosphine, tri-p-tolylphosphine, tri-o-anisylphosphine, and tri-p-anisylphosphine are mentioned. Can be done.

As the phenolic antioxidant, there are high molecular weight phenolic antioxidants and low molecular weight phenolic antioxidants, either of them may be used, or these may be mixed and used.

Examples of the high molecular weight phenolic antioxidant include hindered phenolic compounds. Examples of the hindered phenol-based compound include tris (2-alkyl-4-hydroxy-5-branched C3) such as 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane. Tris (3,5-di-branched) such as -8 alkylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene 1,3 such as C3-8 alkyl-4-hydroxybenzyl) benzene, 1,3,5-trimethyl-2,4,6, -tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, etc. , 5-Trialkyl-2,4,6-Tris (3,5-di-branched C3-8alkyl-4-hydroxybenzyl) benzene, Tetrax [Methylene-3- (3,5-di-t-butyl-) 4-Hydroxyphenyl) propionate] Tetrakiss such as methane [alkylene-3- (3,5-di-branched C3-8 alkyl-4-hydroxyphenyl) propionate] C1-4 alkane, pentaerythrityl tetrakis [3- (3) , 5-Di-t-butyl-4-hydroxyphenyl) propionate] and the like pentaerythrityl tetrakis [3- (3,5-di-branched C3-8 alkyl-4-hydroxyphenyl) propionate] and the like. Commercially available products include those manufactured by Ciba Japan Co., Ltd. and having a trade name of "Irganox 1010" and the like.

Examples of low-molecular-weight phenolic antioxidants include dibutylhydroxytoluene (BHT), butylated hydroxyanisole (BHA), 2,6-di-t-butyl-p-cresol, and 2,6-di-t-butyl-4. -Ethylphenol, 2,6-di-t-butylphenol, 2,4-dimethyl-6-t-butylphenol, 2-methyl-4,6-di-nonylphenol, butylhydroxyanisole, butylated phenol, 2,4 Monophenolic compounds such as 6-tri-t-butylphenol and 4,4'-dihydroxydiphenyl, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl) -6-t-butylphenol), 4,4'-butylidenebis (3-methyl-6-t-butylphenol), 4,4'-butylidenebis (2,6-di-t-butylphenol), 1,1'-bis Bisphenol compounds such as (4-hydroxyphenyl) cyclohexane, 2,2'-dihydroxy-3,3'-di (α-methylcyclohexyl) -5,5'-dimethyldiphenylmethane, 2,5-di-t-butyl Hydroquinone, hydroquinone monomethyl ether, hydroquinone compounds such as 2,5-di- (third amyl) hydroquinone, n-octadecyl-3- (4'-hydroxy-3', 5'-di-t-butylphenol) propionate, etc. Hindered phenolic compounds and the like. In addition, low molecular weight phenolic antioxidants include hydrazine compounds {N, N'-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine having a hindered phenol structure and the like. } And the like are also included.

When adding the above-mentioned antioxidant to the raw material resin, it is preferable to prepare a masterbatch to which these are added as in the case of the above-mentioned inorganic particles, chemical foaming agent and dispersant, and mix this with the raw material resin pellets. That is, pellets (foaming aids) containing inorganic particles, chemical foaming agents, dispersants, and antioxidants are prepared, used as a masterbatch, and mixed with raw material resin pellets.

When pellets (foaming aids) containing all of the above-mentioned additive components are used as a masterbatch, the blending with the raw material resin pellets is the content contained in the pellets (foaming aids) of each component, at the time of molding. It may be decided in consideration of the optimum addition amount of each component.

For example, the amount of inorganic particles such as talc used as a nucleating agent should be 500 to 2000 ppm, the amount of chemical foaming agent (main chemical foaming agent) used should be 560 to 2240 ppm, and the amount of auxiliary chemical foaming agent to be used should be 440 to 1760 ppm. Is preferable. Thereby, the foaming ratio and the bubble diameter can be optimized. The dispersant is preferably 1000 to 4000 ppm. If the amount of the dispersant is less than this, the dispersion may be insufficient, such as aggregation of inorganic particles. On the contrary, if it is too much, no further effect can be expected due to volatilization or the like.

As described above, the total content of the antioxidants must be 300 ppm or more for the amount of the phenolic antioxidants and phosphorus-based antioxidants added, but the optimum amount of each antioxidant is added. be. Specifically, the content of the phenolic antioxidant is preferably 250 ppm to 750 ppm. The content of the phosphorus-based antioxidant is preferably 250 ppm to 3000 ppm.

By setting the addition amount of the phenol-based antioxidant and the phosphorus-based antioxidant within the above range, it is possible to improve the recyclability and moldability in the foam molding of the polyethylene-based resin, which is preferable as a formulation. It becomes. In particular, changes in physical property values (melt tension MT and melt flow rate MFR) before and after the heat history can be suppressed, which is effective in recycling polyethylene-based resins.

The amount of the above-mentioned antioxidant is the content of the antioxidant contained in the final product, the foam blow molded product (here, the foam duct 10). The content of the antioxidant contained in the foam molded product can be quantified by, for example, quantitative analysis using liquid chromatography. Since antioxidants are pure chemicals, they have a unique retention time (which varies slightly depending on the developing medium and column type, but is determined using a standard material), peak area, and high. The sa is proportional to the concentration. Therefore, if a calibration curve is prepared with a standard sample, the concentration can be obtained. In the case of the phenol-based antioxidant and the phosphorus-based antioxidant, the content of the antioxidant contained in the foam-molded product, which is the final product, is substantially equal to the amount added at the time of manufacture.

On the other hand, as for the content of each component in the pellet (foaming auxiliary material) used as a master batch, the addition amount of the phenol-based antioxidant is 1.25 to 3.75% by mass, and the addition of the phosphorus-based antioxidant. The amount is 3,000 to 15.00% by mass, the amount of inorganic particles added is 5.00 to 10.00% by mass, the amount of main chemical foaming agent added is 2.80 to 11.20% by mass, and the amount of auxiliary chemical foaming agent added. The amount of the dispersant added is 2.20 to 8.80% by mass, the amount of the dispersant added is 5.00 to 20.00% by mass, and the ratio of the diluted resin is 31.25 to 80.75% by mass. preferable.

In pellets (foaming aids) used as a masterbatch, it is preferable that the concentration of each component is as high as possible, but when the proportion of diluted resin is less than 31.25% by mass, each component is contained in the pellet. It becomes difficult to knead. On the contrary, if the ratio of the diluted resin exceeds 80.75% by mass, the ratio of the diluted resin in the product may increase, which may have an adverse effect such as deterioration of physical properties.

As described above, various effects can be obtained by using the foaming auxiliary material of the present invention. For example, since there is no dispersion defect, defects due to density unevenness are unlikely to occur. In addition, each component of the nucleating agent functions effectively, and a uniform foaming state with a small bubble diameter can be realized. Further, by packing all the added components in one pellet, the amount of the diluted resin used can be reduced, and the handleability can be improved as compared with the case where all the added components are added individually. In addition, quality control can be performed only by checking the pellets used as the masterbatch, which facilitates quality control.

The same effect can be obtained with the foam molding method of the present invention. Also in the foam molding method of the present invention, it is the optimum embodiment to use pellets containing a nucleating agent, a dispersant, and an antioxidant as a masterbatch, but the present invention is limited as long as these components can be added at the same time. do not have.

Although the embodiments to which the present invention is applied have been described above, it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. It is possible.

Hereinafter, specific examples of the present invention will be described based on the experimental results.

Examination of the optimum amount of added components HDPE [MFR 0.25 g / 10 min (measurement condition 190 ° C., 2.16 kg), density 0.949 g / cm3] 50 parts by weight and LDPE [MFR 1.79 g / 10 min (measurement condition 190 ° C.) , 2.16 kg) Density 0.918 g / cm3] 50 parts by weight of recycled material (recovered resin material of the resin composition containing HDPE and LDPE as the main components) is kneaded and foamed using this as a raw material resin. The duct was formed by blow molding. The raw material resin pellets include a phosphorus-based antioxidant (manufactured by Ciba Japan, trade name Irgafos 168), a phenol-based antioxidant (manufactured by Ciba Japan, trade name Irganox 1010), and a main chemical foaming agent (baking soda). Table 1 shows pellets (foaming aid) kneaded with a particle size of 64 μm), an auxiliary chemical foaming agent (citric acid), inorganic particles (talc or calcium carbonate), and a dispersant (metal soap: 12-hydroxystearate magnesium). It was blended so as to be the amount used as shown in. Table 1 shows the amount of each component used (addition amount), the bubble diameter of the manufactured molded product, and the expansion ratio.

As is clear from this table, by blending the optimum amount of each component, a foam-molded product having a small bubble diameter (cell diameter of 100 μm or less) and a large foaming ratio (average foaming ratio of 2.7 times or more) can be obtained. (Sample Nos. 1 to 4). On the other hand, in the sample lacking any of the components, inconveniences such as a large bubble diameter and a low bubble magnification occur. Further, as the inorganic particles, the addition of talc is effective, the effect is insufficient with calcium carbonate, the bubble diameter is large, and the foaming ratio is also insufficient. Sample No. to which no antioxidant was added. In No. 5, when a crushed material such as a burr was recycled and used, pinholes and the like frequently occurred due to oxidative deterioration, and molding was difficult.

Examination of compounding method For sample 2 shown in Table 1, the difference depending on the compounding method was investigated. That is, when pellets containing all of the antioxidant, inorganic particles, main chemical foaming agent, auxiliary chemical foaming agent and dispersant were added to the raw material resin pellets, and pellets containing each component individually were added to the raw material resin pellets. In each case, foam molding was performed under the same conditions, and differences in the obtained molded products were investigated. As a result, when pellets containing all of the antioxidant, inorganic particles, main chemical foaming agent, auxiliary chemical foaming agent and dispersant are added to the raw material resin pellets, the bubble diameter, foaming ratio, etc. are uniform and uniform. A molded product was obtained. On the other hand, when pellets containing each component individually were added to the raw material resin pellets, the dispersion of each added component was insufficient, and an uneven molded product was obtained.

10 Foam duct 21 Circular die 30 Mold clamping device 31, 32 Divided mold P Parison

Claims (9)

A foaming auxiliary material used for foam molding, which is kneaded together with a raw material resin pellet made of a polyolefin resin and foamed using a physical foaming agent.
Inorganic particles, chemical foaming agent, and dispersant are added to the diluted resin.
A foaming auxiliary material, wherein the diluted resin is LLDPE. The foaming aid according to claim 1, further comprising an antioxidant added to the diluted resin. The foaming aid according to claim 2, wherein a phenolic antioxidant and a phosphorus-based antioxidant are added as the antioxidant. The amount of the phenol-based antioxidant added was 1.25 to 3.75% by mass, the amount of the phosphorus-based antioxidant added was 3,000 to 15.00% by mass, and the amount of the inorganic particles added was 5.00 to 10%. .00% by mass, chemical foaming agent added 2.80 to 11.20% by mass, chemical foaming aid added 2.20 to 8.80% by mass, dispersant added 5.00 to The foaming auxiliary material according to claim 3, wherein the foaming auxiliary material is 20.00% by mass and the ratio of the diluted resin is 31.25 to 80.75% by mass. The foaming auxiliary material according to any one of claims 1 to 4, wherein the inorganic particles are talc. The foaming auxiliary material according to any one of claims 1 to 5, wherein the resin used for the raw material resin pellets is a polyethylene-based resin. The foaming auxiliary material according to any one of claims 1 to 5, wherein the melting point of the resin used as the diluting resin is lower than the melting point of the resin used for the raw material resin pellets. The foaming auxiliary material according to any one of claims 1 to 7, wherein the foaming auxiliary material is in the form of pellets. A foam molding method for molding a foamed resin obtained by foaming a resin material using a physical foaming agent.
A foam molding method characterized by adding pellets prepared by adding inorganic particles, a chemical foaming agent, and a dispersant to a diluted resin made of LLDPE to a raw material resin pellet made of a polyolefin resin and kneading them.

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