KR840000425B1 - Method of manufacturing low density plastic foam products - Google Patents

Abstract

The manufacturing process for low density plastic foam products comprises charging inside a mold 100 wt.% ethylene vinyl acetate copolymer, 20-80 wt.% foaming agent, and 1-5 wt.% cross-linking agent; molding the plastic foams by heating under pressure; cooling the products in the mold; removing the mold.

Description

Manufacturing method of low density synthetic resin foam

The figure is a stress curve diagram comparing the conventional foam and the foam of the present invention.

The present invention relates to a low-density synthetic resin foam having a ethylene vinyl acetate copolymer (hereinafter referred to as EVA) as a main component and a method for manufacturing the same, and a conventional EVA foam is known and has excellent wear resistance bending strength, such as sandal and new windows. It has been mainly used as a material requiring wear resistance.

The foam of EVA has been foamed by adding or mixing a foam crosslinking agent to the ethylene vinyl acetate copolymer of the main raw material and putting it in a molding die, but the foam added here is 3 to 5 parts by weight based on 100 parts by weight of vinyl ethylene acetate. The density of the foam obtained in the above was the limit of 0.2 to 0.4 foaming ratio 5 to 25 at the minimum.

In other words, the foam of EVA is formed by forming a raw material mixed with a foam crosslinking agent into a sheet once, putting it in a mold of about 100 percent, closing it firmly, and heating and foaming it. It was.

However, the EVA foam thus formed shows a significant pressurization state in the mold during the molding process, and when the mold is demolded, the molded foam expands at several times the mold contents.

At this time, the volume ratio of the obtained foam to the volume in the mold is determined by the foaming ratio and the foam density obtained by the amount of the foam blended into the foamed raw material. The amount of 0.2-0.4 foam used has been made into 5-15 weight part with respect to 100 weight part of ethylene vinyl acetate copolymers.

In other words, if a higher foaming ratio and a lower density of foaming agent are obtained, and a large amount of foam is used, the foaming pressure becomes abnormal high pressure in the mold immediately after molding, and the foam is superheated at the high pressure when demolding. There was a problem that the phenomenon of scattering reached, which could not be the desired foam.

In order to avoid the superheat and the scattering of the foam, it is also possible to use a small amount of the foamable raw material sheet filled in the mold and to form voids in the mold, but such a thing only lowers the thermal conductivity at the time of heating foaming. Rather, the bubbles generated by the heating foam escape from the raw material, collect in the mold and study, and at the same time, they degenerate into the atmosphere, resulting in a uniform foam.

Therefore, the foaming of the EVA is filled with about 100% of the sheet-like raw material in which the foam crosslinking agent is mixed in the mold, and the amount of foam is used in order to avoid the superheat and the scattering of the foam during the molding process. A small amount of 15 parts by weight was obtained with low foaming, and the density was 0.2-0.4, which is only an ordinary limit.

As for the mill of the ethylene vinyl acetate copolymer foam which is already used in sandals, soles, etc. which are already commercially available, the foam required for other uses is 0.3-0.9 and the foam required for other uses is at least 0.2. Was in the shape of.

The ethylene vinyl acetate copolymer is particularly excellent in strength and abrasion resistance, and if its high foaming and low density products can be easily obtained, its use is expected to contribute a great deal to various cushions and other industrial materials.

The present inventors have studied to overcome the above problems in the production of EVA foam, and as a result, it has been found that the conventional problem is solved at once as a means for temporarily cooling before demolding the heated foamed body. The invention is completed.

According to one embodiment of the present invention to provide a low density foam of ethylene vinyl acetate copolymer having a density of 0.1 or less, which is 20 to 80 parts by weight of foaming agent, 1.0 cross-linking agent based on 100 parts by weight of vinyl ethylene acetate copolymer in the mold -5.0 parts by weight were added to each of the mixed foam raw materials, and then the mold was closed and closed. Then, the foam was heated to mold the foam. The foam was pressurized in the mold, and then the foamed product was kept in the mold. It is the manufacture of the manufacturing method characterized by opening a molding die after that.

As the main raw material ethylene vinyl acetate copolymer used in the present invention, any compound may be used, but usually 10-40 vinyl acetate is used with respect to ethylene 100, and such a copolymer is added with a foam, a crosslinking agent, and the like. For example, the mixture is kneaded in a roll for 10 minutes to form a sheet.

The blowing agent used here is used as the expectation used in conventional EVA foams. Examples: azodercarbonamide, dinitrosotametarenetetramine, p-tolusfonylhydrazine, azobisinbrotironitrile, diazoaminoazobenzene-tolsulfonylsemicarbazide. These blowing agents are 20 to 80 parts by weight with respect to 100 parts by weight of EVA, preferably 20 to 50 parts by weight.

If it is not filled in 20 parts by weight, a low density foam is not obtained, and if it exceeds 80 parts by weight, the foam is rapidly expanded and a stable foam cannot be produced.

It is one of the features of the present invention that the added amount of the foam is considerably increased in consideration of the conventional use of the blowing agent of 5 to 15 parts by weight.

In addition to the blowing agent, a crosslinking agent is added. Examples of the crosslinking agent include organic solvents such as dichmilperperoxide, 2.5-dimethyl-2.5G (tertiarybutyl) peroxide, 1.3-bis (tishiributylperoxyisopropyl) benzene, and m-octadisyl azideholate. Peroxide.

Although these addition amounts are related to the usage-amount of a foaming agent, they are 1-5 weight part with respect to EVA and 100 weight part, Preferably they are 1-2 weight part. If it does not occupy 1.0 part by weight, crosslinking is insufficient. If it exceeds 5 parts by weight, foaming agent and balance are lost, resulting in unstable foaming.

Other additives include urea, amines, colorants and fillers as foaming aids.

After the mixed raw material is sufficiently kneaded, it is cut into a sheet shape in the form of a sheet and filled into the mold.

The molding die used herein may be any shape, but in the demoulding of the foamed molded article, it is preferable to have an opening of a normal light type because the product is ejected from the mold at once.

The foaming material is filled to the molding die, but it is filled by pressing it slightly, and the mold is firmly fixed by covering the mold. The closing and fixing method can be arbitrarily used, and the mold lid can be opened and closed, and a convenient method for solidifying the closed mold is to use a press machine, and to attach the lid of the mold to the end thereof, thereby closing the mold. After closing with a lid, it is immediately heated and foamed.

The heating temperature is determined by the decomposition temperature of the blowing agent used, and is generally about 160 ° -180 °. Next, in a state where foaming is sufficient, it is cooled as it is once. Here, the cooling temperature is not generally determined by the raw materials used, that is, the degree of vinyl acetate of EVA, the type and amount of the blowing agent, the type and amount of the crosslinking agent, and the like, but is generally 60 to 130 ° C.

This cooling is, for example, forced cooling, such as sending cooling water to a jacket of a mold, but the internal pressure of the filled mold of the EVA foam made by heating foam is thought to decrease, but this is due to the foaming of EVA. It is inferred that this is because the vapor pressure generated at the time decreases temporarily due to the temperature drop.

The molding die is opened through this state. As a result, the EVA foam is demolded from the mold in a state of being cast in the mold. At that moment the volume of the foam expands 15 to 50 times. As a result, the foam of the present invention is formed at one time. In the present invention, the density of the formed foam reaches 0.2 to 0.4, in particular, up to 0.01, in particular up to 0.02-0.05.

In addition, it is 15-50 times in the present invention that it was 2.5-5 times in the conventional expansion ratio.

As described above, since the EVA foam kept in the mold under heating and foam pressurization according to the present invention is cooled before being demoulded, the mold is opened and taken out, thereby reducing the internal pressure of the mold and increasing the universality of the foam. It is possible to produce high foaming and low density foams using a large amount of foam, excluding superheat, scattering and other phenomena in demolding.

The high-foaming, low-density foam produced in the present invention possesses flexibility and also has resilient elastic strength, and its characteristics are not found in existing bubbles such as polyurethane foam and polyethylene foam as shown in the accompanying drawings.

The figure shows a comparison in the case where the amount of bending is set as a stress bending curve (S-S curve) with respect to each bubble of polyethylene 1, this invention 2, and polyurethane 3.

As can be seen by this, the present invention was found to be excellent foam with a low heat loss (Hysteresis Lose).

In addition, the EVA foam has excellent adhesive properties, and the value of the EVA foam is further increased, and it is considered that the EVA foam will be widely used as a vehicle cushion, various cushions, high pressure cushions, and other industrial materials.

Example 1

Among the raw materials, EVA, dichmil peroxide, calcium carbonate, and carbon black were mixed in advance, and then kneaded with a roll having a surface temperature of 90 ° C. for 5 minutes, and then azodicarabolamide was added and kneaded again for 4 minutes to form a sheet having a thickness of 2 mm. It was. 4 sheets of this were placed in a mold of an ordinary shape at 45 mm in length and width and 30 cm in width, and the upper opening was covered and closed with a single plate thereon. The mold was pressed at 150 kg / cm ² pressure at the top and bottom of the press, and heated steam was put into the gel gel of the press as it was, and the mold was heated to 170 ° G for 15 minutes.

After that, the heated steam of the press was removed, and water was added thereto and held for 5 minutes. As a result, the mold temperature reached 80 ° C. Thereafter, the press was opened, and the foam was blown upward from the mold to obtain a foam according to the present invention at one time. The foam had a density of 0.038 and its appearance was the same as that of the mold, and no superheat lamp was generated.

On the other hand, the resilience of the foam was 50% and the tensile strength was 6.9 kg / cm ^{2 as} measured according to JISK 6401. The cotton and the touch were also good, and the other wear resistance and the water absorption were also very good.

Example 2

The compounding ratio was changed as follows, and it grind | pulverized with Example (1).

However, the heating temperature is 10 ℃ lower temperature 160 ℃ than in Example (1) and after foaming, after putting water into the mold operation jack and maintained for 2 minutes, the mold is 75 ℃ and the other operation as in Example (1) The product was taken out of the mold and the foam had a density of 0.040 and the appearance was the same as that of Example (1).

Example 3

The compounding ratio was changed as follows, and it was like Example (1).

However, the cooling holding time was 10 and the mold or 80 degreeC in the meantime. What was obtained was a foam with a density of 0.027.

Example 4

The compounding ratio was changed as follows, and others were carried out as Example (1).

However, it heated and foamed at the heating temperature of 165 degreeC and the pressure of 150 kg / cm <^2> for 20 minutes, and set it as 80 degreeC by water cooling 12 minutes after that. The density of the obtained foam was 0.020.

Example 5

The compounding ratio was changed as follows, and others were performed as Example (1).

However, the mold was opened by heating at 160 ° C for 25 minutes, water cooling for 15 minutes, and holding at 60 ° C.

The density of the obtained foam was 0.018.

According to another embodiment of the present invention, a mixture containing 100 parts by weight of ethylene vinyl acetate copolymer, 5 to 50 parts by weight of polyethylene and / or polystyrene, 20 to 100 parts by weight of a blowing agent, and 1 to 5 parts by weight of a crosslinking agent is used as a foam material. Used.

Polyethylene and polystyrene may be used together with EVA alone, but a combination of polyethylene and polystyrene in an arbitrary ratio may be used in combination with EVA.

If the polyethylene and / or polystyrene is less than 5 parts, the effect of blending polyethylene and / or polystyrene cannot be expected, that is, sufficient improvement in shock absorption of the foam is expected, while polyethylene and / or polystyrene If there are more than 50 parts, strong turnability of cotton will be lost to a bubble, and a cushioning property will become low.

The main raw material is added to a blowing agent, a crosslinking agent and the like and kneaded in a roll for 10 minutes to form a sheet.

The blowing agent is 20 to 100 parts by weight, preferably 20 to 50 parts by weight based on 100 parts by weight of EVA. If it is less than 20 parts by weight, foaming of high foaming and low density is not possible, and if it is 100 heads or more, foam form is scattered during foaming, and signs of scattering appear.

Since the addition amount of a crosslinking agent is related with the usage-amount of a foaming agent, it is 1-5 weight part with respect to 100 weight part of EVA, Preferably it is 1-2 weight part. If this is less than 1 part by weight, sufficient crosslinking is not achieved, and a strong foam is not obtained. On the contrary, if it is more than 5 parts by weight, flexibility is lost.

Other additives include colorants and fillers in addition to urea and amines as foaming aids.

The blowing agent and crosslinking agent may be added in advance in polyethylene and / or polystyrene.

The mixed raw material is kneaded for 10 minutes with a rool or other mixer and then made into a sheet form and cut into a predetermined formation and filled into a molding die.

According to the present invention, the low-density composite foam of the vinyl acetate copolymer and the polyethylene and / or polystyrene produced is remarkable in addition to the repulsive elasticity and the surface strength in order to include polyethylene and / or polystyrene at high foaming and low density. Summer shock absorbency is improved.

Example 6

Among the raw materials, except for the azodicarbonamide, the mixture was kneaded for 5 minutes in a roll having a surface temperature of 90 ° C., and then the azodicarbonamide was added and kneaded again for 4 minutes to obtain a thickness of 2 mm.

4 pieces are placed in molds of 8mm in depth and 25cm in width and 45cm in top openings.The thickness is pressed with a pressure presser at a pressure of 150kg / cm ² . Heat to C and hold for 10 minutes.

Thereafter, the heating steam of the electric press was removed, and water was added and cooled instead, thereby cooling the mold to 95 ° C.

After that, the press was opened, and the foam had been projected upward from the mold at once. The density was measured and found to be 0.022. Its shock absorbency was greatly improved in proportion to conventional foams.

In another embodiment of the present invention, a mixture of 100 parts by weight of an ethylene vinyl acetate copolymer, 5 to 50 parts by weight of polyvinyl chloride resin, 20 to 70 parts by weight of foam, and 1.0 to 5.0 parts by weight of a crosslinking agent is used as the foam raw material.

The secreted chlorine paste is obtained by blending 50 to 150 parts by weight of a plasticizer and 3 to 8 parts by weight of a stabilizer, for example, 100 parts by weight of pest resin.

The ratio of EVA to vinyl chloride dough is 5 to 50 parts by weight based on 100 parts by weight of the former.

If this does not reach 5 parts by weight, the flexibility in the case of adding vinyl chloride cannot be expected. If it exceeds 50 parts by weight, the proportion of EVA decreases, and a foam having a strong cotton strength cannot be obtained.

A foaming agent, a crosslinking agent, and the like are added to the raw material, and the mixture is kneaded for 10 minutes in a roll to form a sheet.

The foaming agent used here is used as it is used for conventional VAE foaming agents and vinyl chloride foaming agents.

The blowing agent is 20 to 70 parts by weight, preferably 20 to 50 parts by weight based on 100 parts by weight of EVA. If it is less than 2 parts by weight, it will not be a high-foaming and low-density foam, and if it is 70 parts or more, the foam will collapse and scatter of foam will appear in the foaming process.

Since the amount of the crosslinking agent added is related to the amount of the blowing agent used, the amount of the crosslinking agent is 1 to 5 parts by weight, preferably 1 to 2 parts by weight based on 100 parts by weight of EVA. If this is less than 1 part by weight, there is no sufficient crosslinking, and a foam having a strong cotton strength is not obtained. On the contrary, if 5 parts by weight is obtained, flexibility is obtained.

Other additives include colorants and fillers in addition to urea and amines as foaming aids.

Among the above additives, a blowing agent and a crosslinking agent may be added in advance to the vinyl chloride paste.

The mixed raw material is kneaded with a roll or other kneader for 10 minutes, then made into a sheet shape, cut into a predetermined shape, and filled into a molding die.

The low density composite foamed product of the ethylene vinyl acetate copolymer and the vinyl chloride resin produced by the method of the present invention includes vinyl chloride as a high foaming and low density, and thus has remarkable flexibility in addition to the resilience and strength of cotton.

Example 7

Kneading the vinyl resin and dioxyl phthalate in the raw material in advance, and then azodicarbonamide was removed, kneaded for 5 minutes in a roll at a surface temperature of 90 ℃, and then kneaded again for 4 minutes by adding azodicarbonamide to a thickness of 2rnrn It was a site.

Cover this with 8 mm deep, 25 cm wide and 25 cm wide top molds, and insert them into a mold of ordinary light type, press the machine with a press of 150kg / cm ² , press the heating machine into the jacket of the press, and heat to 170 ℃. It was kept for 12 minutes.

Then, the heating medium of the press was removed, water was added again to cool, and the mold was cooled to 80 ° C.

After that, the press was opened, and the foam was cast out of the mold at one time.

When the density of this was measured, the outer plane was also uniform at 0.028 g / cm ² . Moreover, it was 6-7 when this was measured with the C type hardness meter. On the other hand, the hardness measurement was carried out in the same manner as in the above Example except that the vinyl resin and zinc stearate in the raw material were removed, and the hardness was 13 to 15.

According to another embodiment of the present invention, a plurality of pore-forming rod-shaped members penetrate the above-mentioned foam raw material to fill in the molding die, and then close the molding die to be heated, and then heat it to form a foam to mold the foam into the mold. A low-density synthetic resin foam characterized by removing the floating member for void formation embedded in the foam raw material from a foam obtained by pressurizing, then cooling, and then opening the overcoat of the molding die and demolding the foam at once. The recipe is provided.

The foamed raw material is kneaded for 10 minutes and then cut into a sheet shape in the form of a sheet, which is filled into a mold at the same time as a plurality of rod-shaped members for forming voids.

In other words, when the sheet-like foamed raw material is filled into the mold, a plurality of pore-shaped rod-like members are inserted through both ends of the raw material body and embedded therein.

Specifically, the foamed raw material sheet is composed of a plurality of sheets, and in the middle of the sheet, a plurality of rod-like members are arranged in parallel or alternately, and again embedded in one or more stages in an arbitrary arrangement. The pore-shaped rod-shaped member used herein may have any shape such as a round oval square or other cross section made of Almi steel, stainless steel or any other metal material or a thermosetting resin material such as meltamine resin or phenol resin.

The thickness is not specifically limited, either. However, it is only necessary to make the length reach the other end surface in the cross section of the foam raw material filled in the molding die.

Example 8

Among the raw materials, EVA, dichmil peroxide and calcium carbonate were mixed in advance and kneaded in a roll having a surface temperature of 90 ° C. for 5 minutes, and then azodicarbonamide was added and kneaded for 4 minutes to obtain a sheet having a thickness of 2 mm.

This was cut into the same size as the mold, and the first two sheets were inserted into a mold having a depth of 8 mm length and width 30 and an upper opening in a mold having a 45 ° C. optical fiber.

Subsequently, a stainless steel round bar having a diameter of 2 mm and a length of 30 cm was arranged at equal intervals for 10 minutes, and two raw material sheets were burned thereon and coated with one sheet of carbon thereon. This mold was pressurized at a pressure of 150 kg / cm ^{2 with} a press machine and heated steam was put into the jacket of the press machine, and the mold was heated to 170 ° C. for 15 minutes.

Thereafter, the heating steam of the press was removed, and water was put therein instead and maintained for 5 minutes. The mold became 80 ° C. Then, when the press was opened, the foam had been projected upward from the mold at a time. Next, it put in this foam previously, and pulled out all the round bars of stainless steel for 10 minutes. The density of this foam was 0.035, and the common diameter of Huhee who pulled out the round bar was 8 mm. In addition, this appearance is the same as the shape in the frame, and no cases such as superheat occurred at all.

On the other hand, the semi-elasticity of this foam was measured in accordance with JIS K6401, and the average was 55%, and the tensile strength was 6.5 kg / cm ² . In addition, the surface strength and touch were extremely good, and the other abrasion resistance and water absorption were also excellent.

Example 9

The compounding ratio was changed as follows, and it carried out like Example (8), and the round bar used was made into the stainless round bar of 3 mm diameter.

However, heating temperature was made into 160 degreeC of 10 degreeC low temperature from Example (8), and after foaming, water was put into the mold sacque and hold | maintained for 2 minutes, and the metal mold | die became 75 degreeC.

The following operation was carried out similarly to Example (8), and the product was taken out from the metal mold | die. This foam had a density of 0.029, which was 12 mm after the round bar was taken out, and the appearance was the same as that of Example (1).

Example 10

The compounding ratio was changed as follows, and it carried out like Example (9), and the round bar used was made into the phenol resin of 2 mm diameter.

100% of EVA (16% of VA contents)

1.3 central parts of bis (tissue tutyl peroxy isopropyl) benzene

AZO di Carbon Amide 30

15 parts of zinc oxide

However, the cooling holding time was 10 minutes and the mold temperature in the meantime was 70 degreeC. The obtained one was a foam having a density of 0.025, and was commonly 10 mm.

According to another aspect of the present invention, after filling a plurality of sheets of the above-described foamed raw material with a release sheet in the middle, the mold is closed, closed and heated to form a foam. The foam is pressurized in the mold and then cooled, and then the molding die is opened to remove the release sheet sandwiched between the foam raw material sheets, thereby providing a method for producing a low density synthetic resin foam. After kneading, this is made into a plurality of sheets, cut into a predetermined shape, and the plurality of sheets are filled in a molding die with the forming sheet interposed therebetween.

A plurality of sheets of this forming sheet are interposed between the sheets on one surface, respectively, and the whole is polymerized to a thickness of the mold depth, and the whole is filled into the mold. As the forming sheet used herein, any of these coarse forming materials, synthetic resin sheets, fabrics, aluminum films, synthetic resin plates, metal plates, and the like may be used. Put it. The thickness of this sheet is not particularly limited, but if it is too thick, there is no room for filling the raw material sheet, resulting in inefficient production. In addition, in this invention, the thin film formed by apply | coating the liquid mold release agent, such as a wax emulsion zone, etc. between a some foaming raw material sheet as a special example of the said release sheet is also included.

The molding die used for the molding of the foamed raw material may be in any form, but in the demoulding of the foamed molded article, it is preferable to have an ordinary light-opening opening because the product is projected out of the mold at once. The foamed raw material is filled to the molding die, but it is filled by pressing it slightly, and the mold is overlaid to fix it firmly. In the demolded foam, the release sheet interposed between the molded raw material sheets is removed. Thereby, the foam is ruptured one by one in the thin film sandwiched between the release sheet and the release sheet, whereby a smooth and extremely thin sheet of 2-3 mm is molded at a time without undergoing a slicing process. As a result, the thin sheet thus formed has a thickness sufficiently uniformly capable of forming foam, so that there is no residual trauma, and there is no case of a fata uneven phenomenon on the flat plate.

According to the present invention, it is possible to manufacture up to 1/500 ~ 1/300 (thickness about 2 ~ 3mm) with a sheet of 1m in length and width, and 1/50 ~ 1/30 (thickness about 20 when not using the present invention). I can manufacture many pieces at one time to a thin thing to 1/10 of -30mm again

Example 11

Among the raw materials, EVA polyethylene, dike mill peroxide zinc stearate, and carbon black were mixed in advance and trained for 5 minutes in a roll having a surface temperature of 90 ° C., and then azodicarbonamide was added thereto, followed by kneading for 4 minutes to form a sheet having a thickness of 1 mm. It was set as. A commercially available release paper was placed in the middle of each of these sheets, and an inner shape of a depth of 8 mm, a length of 270 mm, and a width of 200 mm was inserted in the mold of a normal light type mold at 45 °, and one sheet was covered thereon. .

The mold was heated in a jacket of a press machine, and the mold was heated to 165 ° C. for 15 minutes. Thereafter, the heating steam of the electric press was removed, and water was put therein and held for 5 minutes instead, and the mold became 85 ° C. After that, when the electric press was opened, the foam was blown up and down in the mold to obtain a low density half-cell. When the release sheets interposed between the raw material sheets formed in the foam were removed, the seven sheets were cleanly cured, having a size of 840 × 670 × 3.2 mm and a weight of 0.028. Each of the seven sheets had no residual trauma and no patter irregularities even in the plain view.

Example 12

The raw material was mixed in advance as in Example 11, EVA, Dik Milper Oxide, and calcium carbonate, and azodi carbonamide was added thereto, and kneaded for 4 minutes to prepare a sheet having a thickness of 1.5 mm. After cutting the sheet into the same size as the mold, 0.3mm thin plate was inserted in between to fill a 4 sheet polymerization, mold of 270mm length and 200mm width 7mm depth, and overlaid one shot on it. . The mold was pressurized at a pressure of 100 kg / cm ^{2 with} a press, and heated steam was put into the jacket of the press as it was, and the mold was kept at 170 ° C. for 13 minutes. Thereafter, the heating steam of the press was removed, and water was instead injected into the steam and held for 7 minutes, and then cooled to 80 ° C. Then, when the mold was opened, the foam was blown upward from the mold to obtain an EVA foam. When the thin plates interposed between the raw material sheets were removed from the foam before molding, the four sheets were cleanly cured and each had a size of 630 x 510 x 3.6 mm and a specific gravity of 0.07. There was no residual trauma in each sheet.

The low density foam of the present invention may be produced by a two-stage foaming method as follows. That is, the above-mentioned foam raw material is put in a molding die and heated with a lid, followed by cooling to take out the primary foam from the mold, and the primary foam is put in a separate molding die and heated again to obtain a foam of the final product. . It should be noted that in this two-stage foaming method, the cooling temperature is lower than that of the one-stage foaming method described above, for example, 50 to 100 ° C, and the reheating temperature is also lower than the heating temperature of the foaming method, for example, 100. It is set to -130 degreeC. According to the two-stage foaming method, a foam excellent in dimensional stability and appearance is obtained.

In summary, the gist of the present invention,

1) Fill the mold with a mixture of 100 parts by weight of ethylene vinyl acetate copolymer, 30 to 80 parts by weight of blowing agent, and 1 to 5 parts by weight of crosslinking agent to open and close the mold, and heat it to mold the foam, A method for producing a low density synthetic resin foam, characterized in that the pressurized state in the mold, and then cooled with a sieve held in the mold, and then the cover of the mold is opened.

2) The mixture of the above 1) may be composed of 100 parts by weight of ethylene vinyl acetate copolymer, 20 to 100 parts by weight of blowing agent 1 to 5 parts by weight of crosslinking agent, 5 to 50 parts by weight of at least one of polyethylene or polystyrene,

3) Also the mixture of the above 1) may be composed of 100 parts by weight of ethylene vinyl acetate copolymer, 45 to 50 parts by weight of polyvinyl chloride resin paste, 20 to 70 parts by weight of blowing agent, 1 to 5 parts by weight of crosslinking agent,

4) The mixture of 1), 2) and 3) is molded into a sheet phase,

5) The heating temperature of the above 1) is about 160 ~ 180 ℃,

6) The cooling temperature of the above 1) is about 60-130 ℃,

7) The vinyl acetate content in the ethylene vinyl acetate copolymer of 1), 2) and 3) is 10 to 40% by weight,

8) embedding the rod-like member for space formation in the mixture of 1), 2), and 3) and extracting the rod-shaped member from inside the foam taken out from the mold;

9) a step of sandwiching the mixture of 1), 2), and 3) of the release sheet and a step of removing the release sheet from the foam taken out of the mold;

10) The polyvinyl chloride resin paste of 3) above is 100 parts by weight of polyvinyl chloride resin, 50 to 150 parts by weight of plasticizer and 3 to 8 parts by volume of stabilizer,

11) Cooling after heating in 1), 2), and 3) is lower than the cooling temperature of 6) above to extract the primary foam from the mold, and the foam is put into a separate mold and heated again. And then extracting from the mold to produce a foam,

12) The cooling temperature in the above 11) is 50 ~ 100 ℃,

13) The reheating temperature in 11) is 100 to 130 ° C,

14) a low density synthetic resin foam comprising an ethylene vinyl acetate copolymer according to 1) and having a density of 0.1 or less,

15) a low density synthetic resin foam comprising an ethylene vinyl acetate copolymer and vinyl chloride according to item 3) and having a density of 0.1 or less;

16) The contents of the above items 2) to 16), such as the ethylene vinyl acetate copolymer and the low density resin foam having a density of 0.1 or less and containing at least one of polyethylene and polystyrene according to item 2), are all included in the gist of the present invention. Of course included.

Claims (1)

In the molding die, a mixture of 100 parts by weight of ethylenic vinyl acetate copolymer, 20 to 80 parts by weight of blowing agent, and 1 to 5 parts by weight of crosslinking agent is filled and the coating is closed, and the foam is heated to form a foam. A method for producing a low density synthetic resin foam, characterized in that the foamed molded product is kept in the mold as it is pressurized and then cooled, and then the coating of the molded mold is opened.

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