JPH0130855B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to expandable styrenic polymer particles, and more specifically, it prevents the condensation of the expanded beads during pre-foaming, improves the charging properties of the expanded beads, and particularly improves the charging properties of the expanded beads in a heating mold. This invention relates to expandable styrenic polymer particles that can be molded to shorten the molding cycle to obtain a foam molded product. In the so-called transfer foam molding method for producing foam moldings, when a semi-finished product with an uneven shape obtained from a heating mold is taken out and transferred to a cooling mold, there is little deformation of the semi-finished product and almost no burrs occur. ,
In addition, after the semi-finished product is transferred to the cooling mold, it is not necessary to cool the inside of the semi-finished product to a very low temperature. In the foam molding method, which involves repeated heating and cooling in a mold, it is possible to take out the product without cooling the cooling mold to a very low temperature.At the same time, specifically, it contains a foaming agent. The presence of a mixture of fatty acid and glycerin triesters and diesters and/or triesters, which is rich in monoesters, on the surface of the styrenic resin particles makes it possible to improve the stability during molding. The present invention relates to expandable styrenic resin particles that can greatly shorten the cycle, especially the cooling time, and can further minimize the amount of agglomeration of expanded beads during pre-foaming, and can also have low chargeability. In general, the method used to produce styrenic resin foam moldings is to first heat expandable styrene resin particles with steam in a pre-foaming machine, expand them (pre-foam), and leave them for a certain period of time. After aging, it is filled into a designated mold, heated with steam to fuse the pre-expanded grains, and the mold is heated for 30 to 30 minutes.
A molding method is used in which the foam molded product is extracted by cooling it to about 50°C, that is, a molding method in which heating and water cooling are repeated in one mold.As an improvement to this method, the cooling temperature of the mold is maintained high, and the molding There is a molding method that makes it possible to reduce steam consumption by removing the body, and also uses two molds to perform heating and primary shaping and final shaping (cooling) separately. There are molding methods that can greatly reduce the amount of steam consumed by taking out the molded product without water cooling. There are several molding methods as mentioned above, but in each method, the molding cycle, especially the required cooling time in the mold or the required holding time in the mold, has a significant impact on productivity. Giving is obvious. By the way, several attempts have been made to shorten the cooling time during molding. For example, in JP-A-53-97060, a compound containing an ester of an aliphatic carboxylic acid and an aliphatic alcohol, which does not have a hydroxyl group in its structure and is solid at room temperature, is added to the surface of expandable styrenic resin particles. It is described that the cooling time can be shortened by coating with triglycerides. However, according to research conducted by the present inventors, this method not only causes a significant amount of agglomerated particles during pre-foaming, making it difficult to fill the mold into the mold during the molding process. If the pre-expanded particles contain agglomerated agglomerated particles, they may become clogged in pipes during transportation of the expanded particles. It has been found that there are drawbacks such as difficulty in sufficiently transporting the particles, and the pre-expanded particles are significantly charged, which poses a safety problem. Also, U.S. Patent No. 3789028 describes glycerin-
Coating fatty acid partial ester mixtures is described, specifically 30-60%, 30-60%, 5-20% mono-, di-ester, and tri-ester of glycerin and saturated fatty acids, respectively. %
It is stated that the cooling time during molding can be shortened by using a mixture of I found that I could hardly find anything. The present invention solves the above-mentioned problems, does not cause disadvantages such as condensation of pre-foamed beads and significant electrostatic properties, and also allows the foam to be taken out of the mold at high temperature and released from mechanical restraint. It is difficult for deformation to occur, or even if it is slightly deformed, it is easy to return to its original state quickly.As a result, the cooling time during molding is shortened,
The object of the present invention is to provide expandable styrenic resin particles that can significantly shorten the molding cycle. That is, the expandable styrenic resin particles of the present invention contain 100 parts by weight of styrene resin, 2 to 10 parts by weight of a volatile organic blowing agent, and 0 to 3 parts by weight of a plasticizer such as a solvent having affinity with the styrene resin. On the surface and/or near the surface of the expandable styrenic resin particles containing The blending ratio of ester is preferably 40 to 90% by weight.
It is formed by the presence of at least 0.05 part by weight of an ester of fatty acid and glycerin which is 50-80% by weight. Here, the fatty acid in the ester of fatty acid and glycerin is _C8 to about _C30 , more preferably _C12 to _C22 , specifically lauconic acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, and margarinic acid. It is one or more types of fatty acids such as stearic acid and stearic acid. Mono-esters and tri-esters of fatty acids and glycerin
The reason why the optimum mixing ratio of tri-ester in the mixture of ester or mono-ester, di-ester and tri-ester is limited to 40 to 90% by weight is that if the mixing ratio is outside this range, a foamed molded product will not be obtained. This is because an adverse effect will occur in any of the steps.
That is, when the tri-ester is 90% by weight or more,
This is because the generation of agglomerated particles during pre-foaming is significant, and the amount of charge on the foamed particles increases, making it impossible to maintain production safety, and if it is less than 40% by weight, the effect of shortening the molding cycle is poor. By the way, the appropriate mixing ratio of the mixture of glycerol esters of fatty acids is pure triglyceride and mono-glyceride or mono-glyceride,
It can be easily obtained by mixing a mixture of di-glyceride and tri-glyceride.
That is, triglycerides include natural animal fats and hydrogenated vegetable oils, such as hydrogenated beef tallow, hydrogenated soybean oil, hydrogenated coconut oil, and hydrogenated palm oil.
On the other hand, glycerol esters of fatty acids obtained by the reaction of glycerin and fatty acids (usually resulting in a reaction product mixture of the composition mono-ester, di-ester, tri-ester) or glycerol esters of such fatty acids. The blending ratio of the ester of fatty acid and glycerin, which can be obtained by mixing appropriate amounts of distilled and purified glyceride etc. obtained by suitable distillation and drying from styrene resin to the main body of the expandable styrenic resin particles, is as follows:
The amount is preferably 0.05 to 1.0 parts by weight, more preferably 0.1 parts by weight or more, per 100 parts by weight. The reason for this is that if the blending ratio is less than 0.05 parts by weight, when the foam is taken out from a high-temperature heating mold or a cooling mold that does not reduce the cooling temperature very much, it will be deformed or burrs will occur, resulting in poor molding cycle shortening effect. This is because, if the amount is more than 1 part by weight, the effect of shortening the molding cycle etc. reaches almost saturation, and disadvantages such as deterioration of foaming properties occur. Further, the foamable styrene resin particle main body may contain a cell regulator, an antiblocking agent, etc., if necessary.
The styrene resin refers to a styrene homopolymer and a copolymer resin containing 50% or more of styrene, such as methyl methacrylate, acrylonitrile, α-methylstyrene, butadiene, divinylbenzene, etc. The organic blowing agent contained in the expandable styrenic resin particles is a volatile lower hydrocarbon compound that is liquid or gaseous at room temperature, such as propane, butane,
These include pentane, hexane, etc., and may also contain a small amount of plasticizer for the purpose of improving pre-foaming properties. Examples of this plasticity include ethylbenzene, styrene monomer, xylene, toluene, benzene, hexane, cyclohexane, heptane, and octane. By the way, the type of blowing agent affects the processability of the foam molded product manufacturing process, and in general, compared to blowing agents that are gaseous at room temperature, foaming agents that are liquid at room temperature, such as pentane and hexane, require pre-foaming. Sometimes condensed beads tend to occur. However, in the present invention,
It is effective to use a blowing agent that is liquid at room temperature or a mixture of the liquid blowing agent and a gaseous blowing agent, particularly a liquid blowing agent of 50% by weight or more. In order to further improve the anti-blocking effect, the surface of the styrenic polymer particles or expandable styrene polymer particles is coated in advance with a small amount of metal soap such as zinc stearate, talc powder, wax, silicone oil, etc. Good too. In short, any known manufacturing method may be used to manufacture the expandable styrenic resin particle bodies used in the present invention. Furthermore, the method of making the ester of fatty acid and glycerin exist on the surface and/or near the surface of the expandable styrenic resin particle main body includes mixing the resin particles with the resin particles in a continuous or batch mixer that is usually used industrially. Stir and mix fatty acids and glycerin esters,
Alternatively, a method of fluid mixing, a method of emulsion-forming the ester of fatty acid and glycerin and adhering it to the surface of the resin particles, a method of simply stirring and mixing the resin particles and the ester, or a method of dissolving the ester in a volatile solvent and adding it thereto. The method includes a method of adding the resin particles, stirring and mixing, and then evaporating the solvent to coat the particle surfaces, but is not particularly limited to these methods. Next, Examples and Comparative Examples of the present invention will be shown, which demonstrate that the present invention can shorten the molding cycle of a foamed molded product, that almost no agglomerated particles are generated during pre-foaming, and that the pre-foamed particles It is revealed that the charged potential of the foam is low and the degree of fusion of the foamed molded product is high. In addition, all [%] in Examples and Comparative Examples mean [weight %]. Example 1 100 kg of expandable polystyrene beads containing 6% of a 50/50 mixture of pentane/butane as a blowing agent and having a bead diameter of 1.0 to 1.5 mm were prepared.
Put 100Kg of beads into a batch type ribbon mixer,
Stearic acid triglyceride/stearic acid monoglyceride finely powdered to 200 μ or less = 70/30
100g of the mixture was added and stirred and mixed for 10 minutes. The obtained expandable styrene resin particle composition was pre-foamed using a continuous foaming machine to an apparent density of 20 g/. The amount of coagulum in the pre-expanded beads was measured using a wire mesh with an opening of 10 mm, and the ratio to the foamed beads was calculated. The results are shown in Table 1. After preliminary foaming, the amount of charge on the beads immediately after being air-transported to a storage silo was measured using a current collector potential measuring device. The results are shown in Table 1. After the pre-expanded grains are aged in a storage silo at room temperature for 24 hours, they are molded into products with dimensions of 400mm x 400mm using a fully automatic molding machine.
A partially sealed mold measuring mm x 50 mm was filled with compressed air. Immediately after that, heat mold with 0.8Kg/cm ² G steam, change the cooling time after heat molding, take out the product, measure the molded product dimensions, and find that it is almost the same as the mold within ±3% of the mold size. The cooling time was determined. or,
The degree of fusion bonding was determined by determining the ratio of the foamed particles that were broken at the center of the product and the foamed particles that were broken at the center. The results are shown in Table 1. Example 2 Glycerin ester of stearic acid was converted into triglyceride/di-glyceride/mono-glyceride=
The same operation as in Example 1 was carried out except that the mixture was changed to 100 g with a mixing ratio of 55/20/25. The results are shown in Table 1. Comparative Example 1 The same operation as in Example 1 was carried out except that the glycerin ester of stearic acid was not added. The results are shown in Table 1. Comparative Example 2 The same operation as in Example 1 was carried out except that the glycerin ester of stearic acid was changed to one in which only 100 g of stearic acid triglyceride was added.
The results are shown in Table 1. From these results, it is clear that triglyceride alone causes significant coagulation of the pre-expanded particles and a significant deterioration in charging properties. Comparative Example 3 Glycerin ester of stearic acid was converted into triglyceride/di-glyceride/mono-glyceride=
The same operation as in Example 1 was carried out except that the mixture was changed to 100 g with a mixing ratio of 10/40/50. The results are shown in Table 1. From this result, it is clear that when the mixing ratio of triglyceride is small, there is almost no effect of shortening the cooling time. Example 3 Addition amount of glycerin ester of stearic acid
The same operation as in Example 1 was carried out except that the weight was changed to 500 g. The results are shown in Table 1. Comparative Example 4 The same operation as in Example 1 was carried out except that 10 g of glycerin ester of stearic acid was added. The results are shown in Table 1. From this result, it is clear that if the amount of glycerin ester of stearic acid added is too small, there is almost no effect of shortening the cooling time. Comparative Example 5 Example 1 except that the additives were changed to 100 g of stearic acid triglyceride and 50 g of a conventionally known antistatic agent alkylamine ethylene oxide adduct (Electro Stripper TS-2 manufactured by Kao Soap).
I did the same operation. The results are shown in Table 1. Comparative Example 6 Ethylene oxide adduct of polyhydric alcohol (Denon manufactured by Marubishi Yuka Co., Ltd.) was added as an antistatic agent.
733) The same operation as in Comparative Example 5 was performed except that the amount was changed to 50 g. The results are shown in Table 1. These results show that simply adding a general known antistatic agent to fatty acid triglyceride
The problems involved in all steps up to obtaining a foamed molded article could not be sufficiently improved. Example 4 The same operation as in Example 1 was carried out except that 50 g of zinc stearate was added in addition to the glycerin ester of stearic acid. The results are shown in Table 1.

【table】

[Table] Next, in Examples 5 and 6, the conventional molding method in Example 1 was partially changed, and the effects of the present invention were further confirmed. That is, in Examples 5 and 6, the cooling method in the conventional molding method of heating and cooling using the same mold as in Example 1 was changed, and as shown in Japanese Patent Application No. 54-35428, the cooling water was replaced with a gaseous fluid. By supplying it into the chamber of a synthetic resin foam mold, the mist is injected into the chamber of a mold for molding synthetic resin foam, and the mist is brought into contact with the entire area of the mold, regardless of the shape of the mold. A cooling method was adopted in which the mist was evaporated to remove the latent heat of evaporation from the mold surface to uniformly cool the entire mold. That is, it has the structure shown in the explanatory diagram of FIG. The male and female molds c and d constituting the cavity b of the foam beads to be filled with the filling gun a have a hollow structure, respectively, and a large number of ventilate tube-shaped nozzles g and g are installed at desired locations in the respective chambers e and f. …
(hereinafter referred to as nozzle or ventilate nozzle)
are provided, and at least one of them is arranged so as to intersect the jetting direction of the other nozzles to achieve a turbulent flow effect of the mist within the chambers e and f. And these bench yuri nozzles g, g...
Each has a gas supply pipe h such as air that is open-connected to the nozzles g, g, . Further, above both chambers e and f, there are a number of steam piping j that can discharge heated steam, and when this heated steam is not fed into chambers e and f, there is an intake valve k that can suck in outside air. It is being 1 is a plurality of steam pipes connected to the lower side of both chambers e and f, and is connected to a desired suction air-cooling blower to form a gas suction mechanism. Therefore, after the foam beads are filled into the cavity b by the filling gun a and heated and foamed, air is supplied at a desired pressure to the ventilate nozzles g opened in each chamber e and f.
The cooling water is subjected to the ventilic action of the pressurized air and is turned into atomized water or mist by the ventilic nozzle g and is withdrawn into the chambers e and f, and is evenly distributed over the entire chamber area, forming the male and female molds c, The entire surface inside the chamber d is cooled at the same time. In particular, when a large number of ventilate nozzles g are installed to provide directivity in many directions, the nozzle g
Due to the action of the air blown out from the chamber e,
In the space f, the mist becomes turbulent and acts on the male and female molds c and d, cooling them extremely effectively. The mist uniformly attached to the outer surfaces of the molds c and d can further improve the cooling effect by dissipating the latent heat of vaporization from the mold surfaces. Furthermore, in such a state of mist spraying, if the air-cooled blower is operated to suck in the gas in chambers e and f, the intake valve k opens, sucking in the atmosphere and removing the mist filled in chambers e and f. The water vapor generated from the surface of the mold is effectively sucked in, creating a gas flow and significantly improving the cooling effect. In this way, chamber e by air blower,
The cooling gas suction means in chambers f effectively generates a type of gas flow within chambers e and f, unlike the means for simply feeding only mist to cool molds c and d. The effect of removing latent heat of vaporization from d can be more effectively exhibited. Examples 5 and 6 using the molding method using the above-mentioned mold will be described below. Example 5 First, as a blowing agent, pentane/butane = 50/50
Contains 6% of a mixture with a bead diameter of 1.0 to 1.5.
100 kg of expandable polystyrene beads of mm size were prepared. 100 kg of beads were put into a batch type ribbon mixer, and a mixture of 150 g of stearic acid triglyceride and 150 g of stearic acid monoglyceride, which had been finely powdered to less than 200 microns, was added and mixed with stirring for 10 minutes.
The obtained expandable styrene resin particles were pre-foamed using a continuous foaming machine to an apparent density of 20 g/. Using a wire mesh with an opening of 10 mm, the amount of agglomerated particles was measured as a material that did not pass through the wire mesh, and the proportion of the pre-expanded particles to the expanded particles hung on the wire mesh was calculated. The results are shown in Table 2. After preliminary foaming, the amount of charge on the expanded beads immediately after being air-transported to a storage silo was measured using a current collector potential measuring device. The results are shown in Table 2. The pre-expanded grains were aged in a storage silo at room temperature for 24 hours, and then filled with compressed air into a partially closed mold with product dimensions of 400 mm x 400 mm x 50 mm using a fully automatic molding machine according to the molding method described above. . Immediately after that 0.8
The product was heat-molded with steam at Kg/cm ² G, the cooling time after heat-molding was varied, the product was taken out, the dimensions of the molded product were measured, and the cooling time was determined to be within ±3% of the mold dimension. In addition, the degree of fusion bonding was investigated by determining the ratio of foamed particles that were broken at the center of the product and broken at the center of the expanded particles. The results are shown in Table 2. Example 6 In Example 5, the batch ribbon mixer was
100 kg of expandable polystyrene beads containing 6% of a 50/50 mixture of pentane/butane as a blowing agent and having a bead diameter of 1.0 to 1.5 mm, 65% of stearic acid, and 28% of palmitic acid pulverized to less than 200μ.
%, myristic acid 4%, and other fatty acids 3%, which is a saturated fatty acid triglyceride that is solid at room temperature (hardened beef tallow manufactured by Riken Vitamin Co., Ltd.) 140g,
Add a mixture of 65% stearic acid, 28% palmitic acid, 4% myristic acid, and 3% other fatty acids and monoglyceride (Rikemar S, Riken Vitamin Co., Ltd.) and 50g of zinc stearate, and stir and mix for 10 minutes. The same operation as in Example 5 was carried out except for obtaining expandable polystyrene resin particles. The results are shown in Table 2. Comparative Example 7 The same operation as in Example 5 was carried out except that only 100 kg of expandable polystyrene beads and 50 g of zinc stearate were stirred and mixed in a batch ribbon mixer to obtain expandable polystyrene resin particles. The results are shown in Table 2. Comparative Example 8 In Example 5, 100 kg of expandable polystyrene beads, 30 g of stearic acid triglyceride, and stearic acid diglyceride were added to the batch type ribbon mixer.
The same operation as in Example 5 was carried out except that a mixture of 120 g of stearic acid monoglyceride and 150 g of stearic acid monoglyceride was added and mixed with stirring to obtain expandable polystyrene resin particles. The results are shown in Table 2. Comparative Example 9 The same procedure as in Example 5 was carried out except that a mixture of 100 kg of expandable polystyrene, 5 g of stearic acid triglyceride, and 5 g of stearic acid monoglyceride was put into a batch type ribbon mixer, and stirred and mixed for 10 minutes to obtain expandable polystyrene resin particles. The same procedure as in Example 5 was carried out. The results are shown in Table 2.

[Table] Furthermore, in the following Examples 7, 8, and 9, the effects of the present invention were confirmed when a so-called transfer molding method was adopted. The transfer molding method referred to here, as in Japanese Patent Publication No. 47-14514, separates the "first mold for heating and primary shaping" and the "second mold for final shaping and cooling". Modern Plastics
The transfer molding method is described in detail in the November 1979 issue of International, and more specifically, the molding method is described in Japanese Patent Application No. 53-121152 filed by the present applicant. That is, first, using the styrene-based foamable resin particles described in this application, fill gun 1 with pre-foamed polystyrene resin particles 4 that have undergone a pre-foaming and aging process.
This fills the cavity 3 of the first mold for heating and primary shaping. Note that this first mold has irregularities corresponding to the shape of the foam container to be manufactured. Next, a heat medium such as steam is supplied into the cavity 3 of the first mold (not shown) to heat the filled pre-foamed particles 4 to a temperature higher than the softening temperature and re-expand them, and the expansion force melts the particles. This is then held in the mold for a certain period of time to reduce the expansion force and perform primary shaping to form a semi-finished product 4'. Next, this semi-finished product 4' is placed in the first mold (Fig. 2).
The semi-finished product 4 is then transferred to a second cooling mold (Fig. 4) that can form a cavity of the same shape, rapidly cooled, and finally shaped to obtain a final product 4''. ′ from the first mold (Fig. 2) to the second mold (Fig. 4),
First, the heating male mold 2 is slid and removed from the mold (FIG. 2), and the cooling male mold 6 of the second mold is placed in place of the male mold 2 (FIG. 3). After that,
The semi-finished product 4' is transferred to the cooling male mold 6 of the second mold by pushing it with the piston 5 from the back side of the heating female mold 2' of the first mold. After the transfer is completed, the semi-finished product 4' is held and cooled by the cooling template 6' of the second mold instead of the heating female mold 2', and then the final product 4'' is transferred to the cooling template 6'. 6' and the male mold 6' are opened and taken out. Examples 7, 8, and 9 using the above-mentioned molding method are described below. Example 7 First, as a blowing agent, pentane/butane = 50/50.
Contains 6% of a mixture with a bead diameter of 0.5 to 0.8.
100 kg of expandable polystyrene beads of mm size were prepared. 100 kg of beads were put into a batch type ribbon mixer, and a mixture of 280 g of stearic acid triglyceride and 120 g of stearic acid monoglyceride, which had been finely powdered to less than 200 μm, was added and mixed with stirring for 10 minutes.
The resulting expandable styrene resin particle composition was pre-foamed using a continuous foaming machine to an apparent density of 20 g/. By passing the pre-expanded particles through a wire mesh with an opening of 10 mm, the amount of condensate remaining on the wire mesh was measured, and the ratio to the beads hung on the wire mesh was calculated. The results are shown in Table 3. In addition, Table 3 shows the results of measuring the amount of charge on the beads using a current collecting potential measuring device immediately after they were transferred to a storage silo with a pneumatic blower after preliminary foaming. The pre-expanded particles were aged in a storage silo for 24 hours at room temperature, and then filled with compressed air into a partially sealed first mold with product dimensions of 400 mm x 400 mm x 50 mm using a fully automatic molding machine according to the method described above. . Immediately after that 1.0
Kg/cm ² G steam is used to heat-form the second half of the product, which is then held in the same mold for primary shaping.
The semi-finished product at a temperature of -105°C was immediately transferred into a second incompletely sealed mold and cooled to obtain a final product. After changing the holding time, take out the product, measure the finished state of the molded product and the dimensions of the molded product, and check the mold dimensions by ±3.
% molding cycle was determined. In addition, the degree of fusion was determined by determining the ratio of broken particles at the center of the product and those broken at the center of the expanded particles. The results are shown in Table 3. Example 8 First, as a blowing agent, pentane/butane = 50/50
Contains 6% of a mixture with a bead diameter of 0.5 to 0.8.
100 kg of expandable polystyrene beads of mm size were prepared. Stearic acid 65 is finely powdered to less than 200 μ by putting 100 kg of beads into a batch ribbon mixer.
%, 28% palmitic acid, 4% myristic acid, and 3% other fatty acids.320g of saturated fatty acid triglyceride that is solid at room temperature (hardened beef tallow manufactured by Riken Vitamin Co., Ltd.), 65% stearic acid, 28% palmitic acid, 4% myristic acid, 3% other fatty acids
A mixture of 80 g of saturated fatty acid monoglyceride (Rikemar S manufactured by Riken Vitamin Co., Ltd.) and 100 g of zinc stearate were added and mixed with stirring for 10 minutes.
The same operation as in Example 7 was carried out except for obtaining expandable polystyrene resin particles. Table 3 shows the results.
Shown below. Example 9 In Example 7, 100 kg of expandable polystyrene beads, 275 g of stearic acid triglyceride, and stearic acid diglyceride were placed in a batch ribbon mixer.
The same operation as in Example 7 was performed except that a mixture of 100 g of stearic acid monoglyceride and 125 g of stearic acid monoglyceride was added and stirred and mixed for 10 minutes to obtain expandable polystyrene resin particles. The results are shown in Table 3. Comparative Example 10 The same procedure as in Example 7 was performed except that 100 kg of expandable polystyrene beads and 100 g of zinc stearate were placed in a batch ribbon mixer and stirred and mixed for 10 minutes to obtain expandable polystyrene resin particles. I went there. The results are shown in Table 3. Comparative Example 11 In Example 7, a mixture of 100 kg of expandable polystyrene beads, 200 g of stearic acid monoglyceride, 160 g of stearic acid diglyceride, and 40 g of stearic acid monoglyceride finely powdered to less than 200μ was added to the batch type ribbon mixer in Example 7, and the mixture was stirred and mixed for 10 minutes. The same operation as in Example 7 was performed except that expandable polystyrene resin particles were obtained. The results are shown in Table 3. From the above results, when using the expandable styrenic resin particles obtained by the method of the present invention, it is possible to obtain a foam molded product of sufficiently good quality in the transfer molding method, but the expandable styrenic resin of the present invention When particles are not used, the retention time of the shaped foam in the first mold is extended to ensure smooth movement of the semi-finished product from the first mold to the second mold. If this is not done, the external dimensions will expand significantly, making it impossible to obtain a product with a good external shape. Therefore, it has been found that the expandable styrenic resin particles according to the present invention are particularly suitable for the above-mentioned transfer molding method, and have a remarkable effect of improving the resulting foam molded product.

[Table] From the above results, when using the expandable styrenic resin particles according to the present invention, when compared with the molding method of Example 1, the molding method of Examples 5 and 6 and the molding method of Examples 7 and 9 It is recognized that the cooling time shortening effect is relatively remarkable among each molding method. As is clear from the above, the expandable styrenic resin particles according to the present invention include, on the surface and/or near the surface of the expandable styrenic resin particle body,
It is a mixture of fatty acid and glycerin triesters and diesters and/or monoesters, and is formed in the presence of fatty acid and glycerin esters with a triester blending ratio of 30 to 90% by weight. It has a similar effect. (1) Few agglomerated particles are generated during pre-foaming, and it is easy to fill the mold into a mold and transfer it through a pipe during the molding process. (2) In addition, the degree of fusion in the mold is high, and a strong foamed molded product can be obtained. (3) The pre-expanded particles have a low charging potential and there are no safety issues. (4) The molding cycle of foam molded products can be shortened, and in particular, the cooling time in transfer molding can be significantly shortened.

[Brief explanation of drawings]

Figure 1 is a cross-sectional explanatory diagram of a special mold used in the examples of the present invention, and Figures 2 to 5 are cross-sections of essential parts of the mold used to explain the transfer molding method used in the examples of the present invention. It is a diagram. e, f...Chamber, g...Venture nozzle, h...Air pipe, i...Water pipe,...First
Mold, ... second mold, 4 ... pre-expanded particles,
4'...Semi-finished product, 4''...Final product.

Claims (1)

[Claims] 1 Monoglyceride and triglyceride are added to the surface and/or near the surface of the expandable styrenic resin particle body containing 100 parts by weight of styrenic resin, 2 to 10 parts by weight of a volatile organic blowing agent, and 0 to 3 parts by weight of a plasticizer. Or expandable styrenic resin particles, which are a mixture of monoglyceride, diglyceride, and triglyceride, and contain at least 0.05 part by weight of an ester of fatty acid and glycerin in which the blending ratio of triglyceride is 40 to 90% by weight.