JPS58147438A - Manufacture of foamable resin sheet - Google Patents

Abstract

PURPOSE:To manufacture the titled sheet capable of giving a foamed article having excellent heat resistance, adhesivity, flexibility and appearance, by compounding a curing agent and a foaming agent to a low-molecular weight product obtained by melting a specific rubbery polymer and an epoxy resin, extruding the compounded mixture, and aging the extruded sheet. CONSTITUTION:A reaction product having low melt viscosity (preferably 300- 600 poise after the addition of a curing agent, etc.) and a relatively low molecular weight is prepared by melting a mixture containing (A) 20-70wt% of rubbery polymer composed mainly of a carboxyl-containing polymer which is liquid at normal temperature (e.g. carboxyl-containing acrylonitrile-butadiene copolymer) and (B) 30-80wt% of an epoxy resin. The reaction product is mixed with a curing agent and a foaming agent, extruded to a sheet, and aged to partly proceed the crosslinking reaction and increase the melt viscosity (i.e. to 700-1,100 poise). The heat melting is preferably carried out at 140-200 deg.C for 1-4hr.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a foamable resin sheet using a thermosetting composition.

Red-cell resin sheets have a wide range of uses, including heat insulation materials, sound insulation materials, lightweight materials, floating materials, and sealing materials.When used, they are heated to decompose the foaming agent contained inside to form a foam. It is also attached to the object to be adhered. Therefore, such foamable resin sheets must have good adhesion when heated and foamed, as well as heat resistance and flexibility after foaming.For example, if they become too hard after foaming, they may be difficult to handle or There is a risk of rigid fracture occurring during subsequent processing.

However, among these types of foamable resin sheets, those that use thermosetting resins such as epoxy resins as the resin component are difficult to extrude into sheets after containing a foaming agent and a hardening agent. It is necessary to prevent foaming due to decomposition of the blowing agent and curing and gelation due to the curing agent to prevent deterioration in quality and appearance as a sheet-like molded product.Furthermore, it is necessary to sufficiently advance the crosslinking reaction during heating and foaming to prevent tertiary formation. By creating an original network structure, it is necessary to prevent a decrease in expansion ratio and flexibility due to the destruction of the cell membrane due to a significant decrease in melt viscosity, and for this reason, the conditions for extrusion molding and heat foaming become extremely strict. The selection of materials for the foamable resin composition used in the foamable resin sheet has been severely limited. For example, if a blowing agent with a high decomposition temperature is used to prevent the blowing agent from decomposing and foaming during extrusion molding, heating and foaming will be carried out at a higher temperature, which will inevitably have an adverse thermal effect on the adherend.

Among the methods for producing foamable resin sheets using thermosetting resins, one method that yields relatively good results involves melt-mixing an epoxy resin and a rubbery polymer, mainly a carboxyl group-containing polymer that is liquid at room temperature. A method has been proposed in which a composition obtained by the above method is used as an extrusion molding material.

This method focuses on reacting part or all of the above carboxyl group-containing polymer with the epoxy resin to improve the compatibility between the two and to increase the overall melt viscosity after sheet forming. High molecular weight is achieved through a long reaction at high temperatures. However, even in this method, since the foamable resin composition has a high molecular weight, it is necessary to increase the extrusion temperature.
As a result, it is difficult to prevent foaming, curing, and gelation during molding, and because of its high molecular weight, the crosslinking density caused by the curing agent during heat foaming becomes low, resulting in insufficient heat resistance and adhesive properties of the foamed product. Become.

This invention was discovered through extensive research in view of the above-mentioned circumstances. It has good extrusion moldability, can prevent foaming, hardening, gelling, etc. during molding, and is also capable of preventing the adherend from forming when heated and foamed. The object of the present invention is to provide a method for producing a foamable resin sheet that does not require high temperatures that cause adverse thermal effects and has a foamed structure, heat resistance, flexibility, and adhesiveness.

That is, this invention uses 20 to 70% by weight of a rubbery polymer mainly composed of a carboxyl group-containing polymer that is liquid at room temperature.
A mixture containing 80 to 30% by weight of epoxy resin and 80 to 30% by weight of epoxy resin is heated and melted to produce a relatively low molecular weight extrusion molding reactant, and a curing agent and a blowing agent are blended into this reactant and extrusion molded. The present invention relates to a method for producing a foamable resin sheet, which is formed into a sheet, and further includes aging to allow a portion of the crosslinking reaction to proceed to increase the melt viscosity. □An important feature of the present invention is that the sheet-like molded product after extrusion molding is aged to partially advance the crosslinking reaction and increase the melt viscosity. In other words, the reaction between the carboxyl group-containing rubbery polymer and the epoxy resin is carried out at a relatively low temperature and in a short period of time, and low-temperature extrusion conditions are used that do not cause decomposition and foaming of the blowing agent, and curing and gelation by the curing agent during extrusion molding. Even though the foaming resin composition has a relatively low molecular weight, it is possible to increase the melt viscosity by partially proceeding with the crosslinking reaction during the aging process and forming a three-dimensional network structure to some extent. The decrease in melt viscosity caused by the increase becomes more gradual,
The resulting viscoelasticity of the resin can prevent the cell membrane from being destroyed by the expansion pressure caused by rapid decomposition of the foaming agent. Therefore, the foaming state during heat foaming becomes good, making it possible to provide a foamed product with excellent heat resistance, adhesiveness, flexibility, and appearance.

As mentioned above, the rubbery polymer used in this invention is a rubbery polymer mainly composed of a carboxyl group-containing polymer that is liquid at room temperature, and can be used alone or with other rubbers as desired. It has added quality polymers.

A typical carboxyl group-containing polymer is a carboxyl group-containing acrylonitrile-butadiene copolymer, and its commercially available products include B, F, and Goodr.
Manufactured by ich Chemica1, product name: Haika CTBN (
There is a liquid nitrile rubber containing about 20% by weight of acrylonitrile and an acid equivalent of 0.07 per 100y, number average molecular weight R3600). Rubbery polymers that can be used in combination with such carboxyl group-containing rubbery polymers include similar polymers that are solid at room temperature, such as Nippor 1072 (trade name, manufactured by Nippon Zeon Co., Ltd.), as well as neoprene.

7 such as ethylene-propylene-dicyclopentadiene
Ordinary natural rubber or synthetic rubber can also be used. The rubbery polymer used in combination is 50% by weight in the rubbery polymer.
It is desirable to mix in the following range.

On the other hand, the epoxy resin used with the rubbery polymer preferably contains one or more reactive epoxy groups per molecule on average, including bisphenol type, ether type, novolac epoxy type, ester type, cycloaliphatic type, and Nitrogen-containing glycidyl ethers and the like can be used, and usually those that are solid at room temperature are used, but in some cases, some liquid ones may also be used. Commercially available products of such epoxy resin include Epon $1002 and Epon $1004 manufactured by Shell, and ECN12 manufactured by Ciba.
80, TGIC, EDR736 manufactured by Dow Chemical Company, DIC-EPICLON1030 manufactured by Shell Petrochemical Company
．． DIC-EPICLON4Q3Q, Da'7'7-Mical DEN438, DEN439, Dainippon Ink & Chemicals DIC-EPICLON2QO, D1 (
, EPICLON400. CX-221 manufactured by Chi'77,
Examples include the CX-289.

A mixture of a rubbery polymer mainly composed of a carboxyl group-containing polymer and an epoxy resin has a rubbery polymer of 20%
~70% by weight, preferably 35-60% by weight, and the epoxy resin accounts for 80-30% by weight, and if the rubbery polymer is more than 70% by weight, the heat resistance and adhesiveness of the foamed product after heat foaming will decrease. If the amount is less than 20% by weight, the flexibility of the foam product will decrease.

A mixture of a rubbery polymer and an epoxy resin is heated and melted to cause part or all of the carboxyl group-containing polymer, which is a product of the rubbery polymer, to react with the epoxy resin. At this time, the reaction temperature and reaction time are adjusted so that the melt viscosity of the reaction product is relatively low and the molecular weight is low. It is desirable that the melt viscosity after adding a foaming agent, curing agent, and other additives be 300 to 600 poise. Although it varies depending on the composition of the mixture, the reaction temperature is preferably 140 to 200°C and the reaction time is preferably in the range of about 1 to 4 hours.

The reaction product obtained by heating and melting is once cooled to room temperature, and if necessary, a small amount of the same or different rubbery polymer is blended, and a curing agent and a foaming agent are added thereto to form a foamable resin. Make it a thing.

This viscosity is as described above.

The curing agent used here is preferably one that is stable at room temperature and exhibits activity at high temperatures in order to preserve the resin composition for a long period of time. There are nitrogen-containing compounds that decompose to produce at least one active hydrogen-containing amine. Typical degradable curing agents include mo/urea, polyurea, hydrazide, thiourea, etc. Preferred specific examples include 3-(P-chlorophenyl)-1,1-dimethylurea, 2,4-bis(N,N- (dimethylcarbamide) toluene, dicyandiamide, etc., and these may be used alone or in combination of two or more.

Of course, it is also possible to use other curing agents, such as acid anhydrides, imidazoles, imidacillins, etc. Specific examples include phthalic anhydride, maleic anhydride, dodecylco/% phosphoric anhydride, hexahydrophthalic anhydride, methylnadic anhydride, pyromellitic anhydride, and benzophenonetetracarbohydric anhydride. Acid, dichloroconollic acid anhydride, chlorendic anhydride, 2-methylimidazole, 2-ethyl-4-ethylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-ethylimidazole, 2-
Impropylimidazole, 2,4-diethylimidazole, 2-phenyl-4-methylimidazole, 2-methylimidacillin, 2-ethyl-4-methylimidacillin, 2-phenylimidacilline, 2-undecylimidazole Dacilin, 2-heptadecyl imidacillin, 2-ethylimidacillin, 2-isopropylimidacillin, 2,4-
Examples include dimethylimidacillin, 2-phenyl-4-methylimidacillin, and the like.

The proportion of the curing agent to be used varies depending on the type of epoxy resin and rubbery component and their blending ratio, but it is usually used in a proportion of 0.5 to 130 parts by weight per 100 parts by weight of the resin component.

In addition, as a blowing agent, one is selected that decomposes at a temperature higher than the softening temperature of the resin and does not foam during molding. However, since the resin component used has a relatively low softening temperature, a blowing agent with a particularly high decomposition temperature is selected. There is no need to use it, and general azo compounds, nitroso compounds, hydrazide compounds, etc. can be widely applied. Specific examples include azodicarbonamide, azobisisobutyronitrile, dinitrosopentamethylenetetramine, paratoluenesulfonyl hydrazide, and 4,4-oxybisbenzenesulfonylhydrazide. These may be used alone or in combination, optionally with foaming aids such as urea and metal salts of carboxylic acids.

The proportion of such a blowing agent (or this and a blowing aid) is generally about 1 to 25 parts by weight per 100 parts by weight of the resin, and the foaming ratio after heating is practically about 2 to 30 times. It is better to make it happen.

In addition to the above-mentioned components, various compounding agents can be added to this foamable resin composition as necessary. For example, in order to further improve heat resistance, stabilizers such as phenyl-β-naphthylamine, diphenyl-P-phenylenediamine, ditertiarybutyl-4-methylphenol, paraphenylphenol, calcium stearin, dilaurylthiodipropionate, etc. Anti-aging agents, diesters, ester gums, alkyd resins, coumaron resins, flexible epoxy resins, epoxy resin diluents, etc. are used to accelerate curing during heat foaming or to improve adhesion and flexibility. Adding curing accelerators, rubber vulcanizing agents, etc. for the purpose of completeness, and fillers such as clay, talc, calcium carbonate, silica, barium carbonate, etc. for the purpose of improving sheet formability and reducing costs. can. A color releasing agent and the like may also be added.

The foamable resin composition produced in this way can of course be applied as a material for manufacturing various foam molded products of irregular shapes by filling various heating molds and curing and foaming them by heating. In particular, when the above composition is formed into a sheet and applied as a foamable adhesive sheet, or when this sheet is further applied as a foamed sheet that is cured and foamed by heating, the properties of the above composition are more effectively utilized. It becomes what is given.

Sheet molding can generally be carried out by kneading the above-mentioned foamable resin composition using a mixing roll or an extruder, pelletizing it with a pelletizer if necessary, and extruding it into a sheet using an extruder. The extrusion conditions at this time should be such that the composition does not harden and the blowing agent does not decompose (it may decompose if only slightly).

The thickness of the sheet-like molded product formed by the above extrusion molding is usually about 0.05 to 5+ m, preferably 0.1 to 3 m.
It is assumed to be about n.

In this invention, the sheet-like molded product obtained above is aged to partially advance the crosslinking reaction and increase the melt viscosity. Aging is usually about 40-70℃ and 10-1
It is enough to do this for about 00 hours.

Through this aging, a certain degree of three-dimensional network structure is formed inside the sheet-like molded product, and the melt viscosity is 700 to 1.
100 poise, improves the foaming state during subsequent heating and foaming, and greatly contributes to improving the heat resistance, adhesion, flexibility, and appearance of the resulting foamed product.

The foamable adhesive sheet obtained through such aging has good flexibility and has the property of bonding when heated. In use, this sheet may be inserted between adherends and heated by any means such as press heating, far infrared heating, hot air heating, etc. to harden and foam. As a result, a cured adhesive layer with a foam structure is formed that has heat retention, noise, and weight reduction functions. This foam adhesive layer has excellent adhesion or adhesion to the adherend, has good heat resistance, and has excellent flexibility before curing and foaming.

Applicable adherends may be those that do not undergo thermal deformation during curing and foaming, such as aluminum plates, stainless steel plates,
A wide range of materials include metal plates such as steel plates, inorganic boards such as slate plates and magnesium carbonate plates, synthetic resin plates, paperboard, and plywood.

In addition, in conventional thermosetting compositions, foaming agents with high decomposition temperatures are used in order to suppress the decomposition of the foaming agent during sheet molding. In contrast, the composition of the present invention is not subject to such restrictions regarding the blowing agent as described above, and therefore general curing and foaming conditions can be applied, resulting in The range of application can be expanded accordingly.

A composite made by using such an adherend and bonding it with the foam adhesive layer described above can be used as a more practical heat insulating material, a shimmering material, and a lighter weight material than before due to the characteristics of the foam adhesive layer. wood,
It can be used as a floating member, a sealing material, etc.

On the other hand, in this foamable resin sheet, the resin that softens and flows during extrusion molding may undergo molecular orientation, so it shrinks in the extrusion direction at the initial stage of hardening and foaming, and this dimensional change reduces the adhesive area and commercial value. It may be reduced. In such cases, it is usually best to use the foamable resin sheet by adhering it to the reinforcing material. The reinforcing material has the function of preventing waste retention at the initial stage of curing and foaming, and also has the function of directing the three-dimensional expansion force caused by foaming only in the thickness direction, so the dimensions of the adhesive layer after curing and foaming are This gives very good results in terms of stability.

The reinforcing material used here is preferably one made of cheesecloth, a coarse sheet made of various materials, a mesh material such as metal, or a porous material such as woven fabric or nonwoven fabric made of various materials. With such a porous material, even if the foamable resin sheet is placed on only one side of the material, the foamable resin sheet can be transferred from one side to the other side when it is bonded together or when it is cured and foamed during use. Because it can be impregnated and transferred towards 1. The bond between the reinforcing material and the resin sheet becomes strong, so that the reinforcing material can more effectively perform its functions.

From this point of view, when using the above-mentioned net-like material, the size of the mesh should generally be 0.5 mm or more in both the vertical and horizontal directions, preferably in the range of 1 to 10 mm. For those made of other porous materials such as non-woven fabrics and woven fabrics, those having an appropriate thickness or density depending on the material may be used from the same viewpoint as above and also taking into account its mechanical strength.

In addition to such porous materials, materials made of materials substantially free of pores, such as metal sheets such as copper foil and aluminum foil, and plastic sheets, can also be used as reinforcing materials. In this case, generally foamable resin sheets may be placed on both sides of these reinforcing materials.

Methods for adhering and integrating the foam resin sheet with the reinforcing material include, for example, pressing and laminating the foam resin sheet while retaining its softened state immediately after melt extrusion, or bonding the foam resin sheet with a pre-manufactured foam resin sheet. A method such as laminating and integrating the reinforcing material with a thermocompression laminator at a temperature lower than the curing temperature or the decomposition temperature of the foaming agent can be adopted.

In this way, this foamable resin sheet can be bonded and integrated with a reinforcing material to prevent shrinkage at the initial stage of hardening and foaming, and to have a high degree of dimensional stability.
Furthermore, in order to increase the utility value of this type of resin sheet, a pressure-sensitive adhesive is applied to one side of the resin sheet with or without reinforcing material to create a pressure-sensitive adhesive bond to the adherend. It is also possible to use a foamable resin sheet that can be finally cured and foamed.

The pressure-sensitive adhesives used here include a wide variety of conventionally known pressure-sensitive adhesives. It is preferable to use a so-called thermosetting type material which has a thermosetting function when heated and is disclosed in Japanese Patent Publication No. 50-12464 and Japanese Patent Publication No. 50-33702.

Next, regarding the foam sheet, the sheet-shaped molded product mentioned above is not used as it is as an adhesive sheet, but is subsequently placed on a release plate and subjected to various treatments such as far-infrared heating, hot air heating, press heating, etc. By heating and curing and foaming, a foamed sheet product that can itself be used as a heat insulating material, a cooling material, a lightweight material, a floating member, a sealing material, etc. is obtained.

Like the foam adhesive layer formed by curing and foaming the foamable resin sheet, this foam sheet has excellent heat resistance and also maintains good flexibility before curing and foaming, and thus has both characteristics. A foamed sheet with both functions has never been available before.

In addition, when forming such a foamed sheet, if an uncured, unfoamed molded sheet placed on a release plate is laminated to the reinforcement +K and rubbed once to harden and foam, it will adhere to the reinforcing material. A foamed sheet is obtained. The function of the reinforcing material here is the same as in the case of the foamed camellia one-finger sheet, which gives good results for the dimensional stability of the foamed sheet.

When laminating the reinforcing material, there are two cases in which the uncured, unfoamed molded sheet and the reinforcing material are crimped and laminated in advance in the same manner as in the case of the foamed resin sheet, and two cases in which the two are simply stacked together. In the latter case, the adhesiveness of the molded sheet is utilized during the curing and foaming process to bond and integrate the reinforcing material.

The reinforcing material can be made of a porous material such as a net, woven fabric, or non-woven fabric as described above, or made of a material with substantially no pores such as a metal sheet or a plastic sheet. In the case of a material made of the latter material, an uncured, unfoamed molded sheet is laminated on at least one side of the material, and in the case of the latter material, an uncured, unfoamed molded sheet is laminated on both surfaces of the material.

The present invention will be specifically illustrated below with reference to Examples.

In the examples, all parts are by weight.

Example 1 60 parts of Epicote*1001 (bisphenol A epoxy resin, trade name manufactured by Yuka Shell Co., Ltd.) and Hiker CTB
40 parts of N (carboxyl group-containing rubbery polymer, trade name manufactured by Ube Industries, Ltd.) were heated at 180°C in a heated reaction vessel at 3° C.
The reaction between the two was completed by mixing for a period of time, and the reactant was cooled to room temperature to form a lump.
rrtm, load 1o.

The viscosity was measured at 120°C and found to be 450 poise.

Next, 1 part of dicyandiamide was added to 100 parts of the above reactant.
0 parts, 2 parts of imidazole and a blowing agent (Neocelvon P
#1000 (trade name, manufactured by Hyoso Kasei Co., Ltd.) was blended and kneaded using a mixing roll to obtain a foamable resin composition. The melt viscosity of this composition was 500 poise. Subsequently, this foamable resin composition was extruded using an extruder at a die temperature of 85° C. to form a sheet-like molded product with a thickness of 0.8 mm. Next, this sheet-like molded product was aged at 50° C. for 36 hours to obtain a foamable resin sheet. The melt viscosity of this sheet was 750 poise.

The resulting foamable resin sheet had good flexibility, was free from rigid fracture during handling, had a uniform thickness, and had an excellent appearance.

Comparative Example 1 The same amounts of the epoxy resin and carboxyl group-containing rubbery polymer used in Example 1 were mixed and reacted at 180° C. for 4.5 hours, and after the reaction, the mixture was cooled to room temperature to form a lump. The viscosity of this reaction product was measured in the same manner as in the example and was found to be 1000 poise. Next, the same amount of the same additive as in the example was added to this reaction product and cross-mixing was performed to obtain a foamable resin composition with a melt viscosity of 900 voids. This composition could not be easily extruded at a die temperature of 85°C in Example 1, so it was extruded at a die temperature of 110°C to form a sheet-like product with a thickness of 0.8°C, and this was made into a foamable resin. It was made into a sheet. This product showed progress in gelation and hardening, did not have sufficient flexibility, and had a somewhat uneven thickness due to partial foaming, resulting in poor appearance.

Comparative Example 2 The sorted molded product after extrusion molding in Example 1 was made into a foamable resin sheet as it was without aging.

Example 2 43 parts of Araldite GY-6084 (bisphenol A epoxy resin, trade name manufactured by Ciba Corporation) and Hiker CTB
57 parts of N (described above) were mixed and reacted at 180° C. for 2 hours in a heating reaction vessel, and after cooling, the viscosity of the reactant was measured in the same manner as in Example 1 and found to be 350 voids.

At the same time, 25 parts of dicyandiamide, 5 parts of 3-(P-chlorophenyl)-1·l-dimethylurea, and 10 parts of a blowing agent (Vinihole AK#2, trade name manufactured by Hyoso Kasei Co., Ltd.) were added to 100 parts of this reactant. The ingredients were blended and kneaded using a mixing roll to obtain a foamable resin composition with a melt viscosity of 450 poise. Subsequently, this was extruded using an extruder at a die temperature of 70°C to form a sheet-like molded product with a thickness of 1 inch. Next, this sheet-shaped molded product was aged at 60° C. for 72 hours to obtain a foamable resin sheet with a melt viscosity of 800 poise.

The resulting foamable resin sheet had good flexibility, was free from rigid fracture during handling, had a uniform thickness, and had an excellent appearance.

Comparative Example 3 The sheet-like molded product after extrusion molding in Example 2 was made into a foamable resin sheet as it was without aging.

Expandable trees obtained in the following Examples and Comparative Examples.

When the fat sheet was heated at 150° C. for 30 minutes to foam, the results shown in the following table were obtained. The evaluation items listed are based on the measurement method and evaluation index below.

Expansion ratio> It was carried out according to JIS-6767. That is, the apparent foamable sheet density was set as D11 and the apparent foamed sheet density as D2, and the apparent foaming ratio p l/T)2 was calculated.

Flexibility〉 If the surface of the foam sheet is not sticky and is highly flexible, ◎, if it is flexible with some stickiness, ○, if the surface is sticky but still flexible. It was evaluated as △, and the case where rigid fracture occurred and it was difficult to handle was evaluated as ×.

<Heat resistance> The heating dimensional change rate (S1%) of the foam sheet was calculated according to JIS-6767. Also, the appearance.

The presence or absence of changes in shape was also evaluated. The measured temperature is 12
The temperature was 0°C.

Adhesion> It was conducted according to Jll-6854. That is, an aluminum plate (25X 150X 0.2
The adhesion strength between the aluminum plates was measured using the following method. The method involved sandwiching and fixing a foam sheet between adherends, and heating and adhering them in an open atmosphere at 150'C for 30 minutes. Thereafter, it was left to stand at room temperature for 2 hours or more, and a T-peel test was conducted using an Instron type tensile tester at a temperature of 23° C. and a tensile rate of 50 IIllllI/min.

<Appearance> Evaluation was made based on the cell structure of the sheet after heating and foaming and the unevenness of the sheet surface. In other words, when the bubbles are dense and the surface of the foam sheet is uniform, ◎, when the bubbles are dense but unevenness is seen on the surface of the foam sheet, ○ is when the bubbles are coarse and the appearance is poor. The case was rated as △, and the case where the bubbles were coarse or broken and was unusable was rated as ×.

As is clear from the results of the previous examples, according to the present invention, a rubbery polymer mainly composed of a carboxyl group-containing polymer, which is liquid at room temperature, and an epoxy resin are heated and melted to react with each other to form a relatively low molecular weight polymer. A reactant for extrusion molding is produced, and a composition in which this reactant is blended with a curing agent and a blowing agent is extruded into a sheet shape, and then this is aged to allow a portion of the crosslinking reaction to proceed and reduce the melt viscosity. Since the foamed resin sheet has good extrusion moldability and excellent flexibility and appearance, the foamed product obtained by heating and foaming this foamable resin sheet has a good foaming state. It has excellent properties such as flexibility, heat resistance, and adhesiveness, as well as excellent appearance.

Claims (1)

[Claims] (1) A relatively low-molecular-weight extrusion molding reactant obtained by heating and melting a mixture containing 20 to 70% by weight of a rubbery polymer mainly composed of a carboxyl group-containing polymer that is liquid at room temperature and 80 to 30% by weight of an epoxy resin. and this reactant ζ
A method for manufacturing a foamable resin sheet, which comprises blending a curing agent and a foaming agent, extrusion molding the resulting sheet to form a sheet, and roughly aging to partially advance the crosslinking reaction to increase the melt viscosity. .