JPH06171001A - Sheet material for reinforcing panel and vehicle outer panel using the same - Google Patents

Abstract

PURPOSE:To obtain a reinforcing foamed sheet having excellent oil surface stickiness, good heat resistance and lightweight properties by forming a first layer from a plastisol compsn. composed of a copolymer of alkyl acrylate and a radical polymerizable unsaturated carboxylic acid monomer. CONSTITUTION:A first layer is formed from a foamable plastisol compsn. based on a resin obtained by adding a monovalent-trivalent metal cation to an acrylic acrylate (a) and a radical polymerizable unsaturated carboxylic acid monomer and containing alkyl acrylate (a) as a main constitutional unit, an epoxy resin, a plasticizer, a high temp. decomposable foaming agent and a heating activation type curing agent for the epoxy resin. A second layer 2 composed of fiber cloth is laminated on the first layer to obtain a panel reinforcing sheet material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a panel-reinforcing sheet material obtained by heating and processing a plastisol composition having good storage stability, and a vehicle outer panel panel structure using the same.

[0002]

2. Description of the Related Art Metal panels are widely used as structures in various industrial fields such as automobiles, buildings and furniture. Although this metal panel has characteristics of excellent strength and durability, it has drawbacks such as high specific gravity and poor thermal insulation due to good thermal conductivity.

On the other hand, in recent years, from the viewpoint of saving resources and energy, vehicles and building materials have been made thinner and lighter, but on the contrary, the strength is reduced, and for example, for doors of automobiles. In this case, there is a problem in that the tensile rigidity of the surface is insufficient due to the decrease in strength, and the solid feeling as a component is unavoidable.

In order to solve such a problem, for example, a method has been proposed in which a sheet containing an epoxy resin as a main component is attached to a part of a door panel and cured in a paint drying oven of an automobile to reinforce the door. (Actual exploitation 55-10165
No. 9). However, this method has a drawback that a sufficient reinforcing effect cannot be obtained only by sticking it on a part, and conversely, if it is stuck on the entire surface, the purpose of weight reduction cannot be achieved.

In automobiles and building materials, a heat insulating material such as glass wool, felt and urethane foam is provided on the back surface of the panel as a method for preventing heat from flowing in and out from the outside. However, although this method is effective for enhancing the cooling effect and preventing dew condensation, there is a problem in that the heat insulating material used is a large pre-molded product, which requires a long time for installation work.

As a method for solving such a problem, various methods for manufacturing a vehicle outer panel structure having good workability, light weight, and having both heat insulating property and reinforcing property have been proposed.

Japanese Unexamined Patent Publication (Kokai) No. 63-272515 discloses a foaming composition comprising vinyl chloride resin, a plasticizer, a high-temperature decomposition type foaming agent, an epoxy resin and a heat-activatable curing agent for epoxy resin as essential components. A method has been proposed in which a sheet in which one layer, a second layer made of a fiber cloth, and a third layer made of a metal thin film are laminated is attached to the back surface of the panel and then heated to foam and cure.

Further, in Japanese Patent Laid-Open No. 63-28475, in order to improve a firm feeling due to high rigidity, a plastisol composition comprising a vinyl chloride resin for a paste, a plasticizer, a foaming agent, etc. is used as a liquid epoxy resin and a heating agent. A method has been proposed in which an active type curing agent is contained and applied on the back surface of the panel or attached as a semi-gelled sheet, and then heated to foam and cure.

However, although vinyl chloride plastisols have advantages such as excellent mechanical properties, processability, cold resistance, foaming property, flame retardancy, long-term storage stability at room temperature, and low cost, they are especially heated at high temperatures. It has the drawback of generating hydrogen chloride gas from time to time, which is not preferable in terms of safety and hygiene and environmental pollution.

Further, in any of the methods, since the vinyl chloride resin is used as the thermoplastic resin in the foamable composition, the oil surface tackiness is poor. In addition, since the sheet obtained by foaming and curing is inferior in heat resistance, it can be applied to the vehicle outer panel after electrodeposition coating, but cannot be applied to the vehicle outer panel before electrodeposition coating. It has certain drawbacks.

JP-A-51-71344 and JP-A-52-42590 propose plastisols containing an (meth) acrylic acid alkyl ester polymer and an ester plasticizer as essential components. However, although these plastisols do not have the drawbacks of vinyl chloride plastisols, the polymers are dispersed in a general-purpose ester plasticizer such as 2-ethylhexyl phthalate (DOP) which is commonly used for vinyl chloride plastisols. In plastisol, the compatibility of both is poor, and in order to solve this, tricresyl phosphate (T
CP), butylbenzyl phthalate, acetyltributyl citrate and expensive plasticizers must be used. Further, since these plasticizers have a large polarity and have an action of swelling the polymer, there is a drawback that the viscosity of plastisol remarkably increases during storage. The compatibility between the poly (meth) acrylic acid alkyl ester and the general-purpose ester plasticizer can be improved by using a large alkyl group as the acrylic acid alkyl ester or methacrylic acid alkyl ester to be copolymerized ( Japanese Patent Publication No. 62-3868). However, the plastisol prepared by using such a copolymer also has a drawback that the viscosity of the plastisol increases remarkably during storage and may gel at room temperature.

Generally, the storage stability of plastisol tends to be improved by coarsening the dispersed particles, but in this case, the gelling performance of plastisol is lowered, and as a result, the appearance and the appearance of the heat-formed sheet are reduced. It causes an unfavorable situation such as deterioration of mechanical properties.

As a plastisol resin particle having good storage stability, Japanese Patent Laid-Open No. 63-95248 discloses a finely divided copolymer obtained by reacting a carboxyl group-containing copolymer with a polyfunctional basic substance. ing. However, this method was not an essential solution to the problem because the plasticizer was limited to expensive materials such as TCP having large polarity.

As described above, the plastisol using the poly (meth) acrylic acid alkyl ester and the general-purpose ester plasticizer satisfies both the mechanical properties of the sheet after heat molding and the storage stability as the plastisol. There was nothing. In particular, plastisol that satisfies the heat resistance and oil surface tackiness of the sheet after heat molding and can be applied to the vehicle outer panel before electrodeposition coating cannot be made and stored because the viscosity increases remarkably during storage. However, it has been a major obstacle to improving the productivity of vehicle outer panel.

By the way, in the automobile industry, it is strongly desired to provide a reinforcing sheet material on a vehicle outer panel before electrodeposition coating from the viewpoints of improving productivity and expanding use sites. As the reinforcing sheet material provided on the vehicle outer panel before electrodeposition coating, since the rust preventive oil is usually applied to the outer panel before electrodeposition coating, it has excellent oil surface adhesion and What has heat resistance which withstands the temperature of (degree C) or more (temperature at the time of electrodeposition coating) is desired.

[0016]

Under these circumstances, the present invention is excellent in oil surface tackiness, and also has good heat resistance, heat insulating property, reinforcing property, and light weight property by foaming and hardening by heating. It is possible to provide a reinforcing foam sheet having the following properties, particularly a panel material having good workability, which is suitable for reinforcing a metal panel before electrodeposition coating, and a heat insulating property and rigidity reinforced by using the sheet material. It is an object of the present invention to provide an excellent and lightweight vehicle outer panel structure (hereinafter sometimes referred to as a reinforcing material).

[0017]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted intensive studies to develop a sheet material for panel reinforcement and a vehicle outer panel structure having the above-mentioned preferable properties, and as a result, a foamable plastisol having a specific composition has been obtained. A panel reinforcing sheet material having a structure in which a first layer made of a composition, a second layer made of a fiber cloth, and optionally a third layer made of a metal thin film having a specific thickness are laminated, and a vehicle made of the sheet material. Provided on the back surface of the outer panel so that the first layer surface of the sheet material is in contact,
It has been found that a vehicle outer panel structure formed by heating, foaming and curing can meet the purpose, and based on this finding, the present invention has been completed.

Thus, according to the present invention, (a) (a) an acrylic acid alkyl ester and / or a methacrylic acid alkyl ester and (b) a radical-polymerizable unsaturated carboxylic acid monomer are contained, and (a) is mainly contained. 1 to 3 is added to the acrylic copolymer (A-1) which is a constituent unit and optionally contains at least one monomer (c) selected from a diene compound, an aromatic vinyl compound and a vinyl cyan compound. A resin obtained by adding a valent metal cation (A-2), (B) an epoxy resin,
A first layer made of a foamable plastisol composition containing (C) a plasticizer, (D) a high temperature decomposition type foaming agent and (E) a heat-activatable curing agent for an epoxy resin as essential components, and a second layer made of a fiber cloth. A panel reinforcing sheet material having a structure in which a layer and, if necessary, a third layer made of a metal thin film having a thickness of 100 μm or less are laminated, and the panel reinforcing sheet material is provided on the back surface of a vehicle exterior panel. There is provided a vehicle outer panel structure, which is provided so that the first layer surfaces thereof contact each other, and is heated to foam and cure. Hereinafter, the present invention will be described in detail.

In the foamable plastisol composition used for the first layer of the panel reinforcing sheet material of the present invention, (a) an alkyl acrylate and / or an methacrylic acid alkyl ester and (b) a radical polymerizable unsaturated Acrylic consisting of a carboxylic acid monomer, (a) as a main constituent unit, and optionally containing at least one monomer (c) selected from a diene compound, an aromatic vinyl compound and a vinyl cyan compound. In the system copolymer (A-1),
A resin (A) composed of an ionically crosslinked product obtained by ionically crosslinking a free carboxyl group by ionically bonding a free-radical carboxyl group by adding a monovalent metal cation (A-2) is used. Examples of (a) include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2- Examples thereof include acrylic acid alkyl esters such as ethylhexyl acrylate and n-octyl acrylate, and corresponding methacrylic acid alkyl esters. These may be used alone or in combination of two or more. Of these, methyl methacrylate is particularly preferable.

The radically polymerizable unsaturated carboxylic acid monomer (b) in the copolymer (A-1) of the present invention has at least one free carboxyl group for ionic crosslinking per molecule. Examples of such compounds include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, cinnamic acid, maleic acid, itaconic acid, fumaric acid, citraconic acid,
Unsaturated dicarboxylic acids such as chloromaleic acid and its anhydrides and unsaturated dicarboxylic acids such as monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, monomethyl itaconate, monoethyl itaconate and monobutyl itaconic acid. Examples thereof include acid monoesters and derivatives thereof. These may be used alone or in combination of two or more. Among these, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, and itaconic acid are particularly preferable.

Examples of at least one monomer (c) selected from a diene compound, an aromatic vinyl compound and a vinyl cyan compound, which is optionally used in the copolymer (A-1) of the present invention, are: Conjugated diene compounds such as butadiene, isoprene, 1,3-pentadiene, cyclopentadiene, dicyclopentadiene Styrene, aromatic vinyl compounds such as α-methylstyrene Acrylonitrile, vinyl cyanide compounds such as methacrylonitrile 1,4-hexadiene, Examples include non-conjugated diene compounds such as ethylidene norbornene. These may be used alone or in combination of two or more. Of these, butadiene, isoprene, styrene and acrylonitrile are particularly preferable.

In the copolymer (A-1) of the present invention,
(a) a unit formed from the acrylic acid alkyl ester and / or the methacrylic acid alkyl ester,
(b) a unit formed from a radically polymerizable unsaturated carboxylic acid of a unit, and (c) a diene compound of the unit, the content ratio of a unit selected from an aromatic vinyl compound and a vinyl cyan compound is not particularly specified, 60 to 99% by weight of (a) unit based on the total amount of each unit, preferably 70 to 90
Within the range of 0.5% by weight, the unit (b) is 0.5 to 20% by weight, preferably within the range of 0.5 to 5% by weight, and the unit (c) is 0 to 0% by weight.
It is desirable to use within the range of 40% by weight, preferably 0 to 25% by weight.

When the content of the unit (b) is less than 0.5% by weight, it is difficult to suppress the change with time of the viscosity of plastisol. On the other hand, if it exceeds 20% by weight, the compatibility with the plasticizer (C) is lowered, so that the toughness of the foam after heat curing is reduced. As a result, the impact resistance of the reinforcing material decreases.
Further, when the content of the unit (c) exceeds 40% by weight, the viscosity of the resin (A) in the expandable plastisol composition at the time of melting is lowered, and it becomes difficult to obtain a dense cell foam.

If desired, the copolymer (A-1) of the present invention may contain other monomer units copolymerizable with the above-mentioned monomers, as long as the object of the present invention is not impaired. Good. In this case, the content of the other monomer unit is usually 2% in the copolymer.
It should be 0% by weight or less. Examples of such a monomer include a functional group-containing unsaturated monomer for improving the adhesiveness of the foamable composition, specifically, glycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl ( Polymerizable unsaturated compound having an epoxy group such as (meth) acrylate and cyclohexene monoxide 2-aminoethyl (meth) acrylate, 2-aminopropyl (meth) acrylate, 3-aminopropyl (meth) acrylate, 2-aminobutyl ( (Meth) acrylate, 3-aminobutyl (meth) acrylate, 4
-Aminobutyl (meth) acrylate, (meth) acrylamide, N-2-aminoethyl (meth) acrylamide, N-2-aminopropyl (meth) acrylamide,
Amino group-containing polymerizable unsaturated compounds such as N-3-aminopropyl (meth) acrylamide 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxy Examples thereof include a hydroxyl group-containing polymerizable unsaturated compound such as butyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and dipentaerythritol hexa (meth) acrylate. These other copolymerizable monomers may be used alone or in combination of two or more.

The molecular weight of the copolymer (A-1) of the present invention is
The average molecular weight is not particularly limited and is usually 100.
000 to 1500000, preferably 20
It is in the range of 0000 to 1,000,000.

The copolymer (A-1) of the present invention is preferably produced by a fine suspension polymerization method, an emulsion polymerization method or a seed emulsion polymerization method which is commonly used in the production of a vinyl chloride paste processing resin. However, when a material having a relatively large particle size to be blended for the purpose of reducing the sol viscosity is required, the suspension polymerization method or the bulk polymerization method is advantageous.

The fine suspension polymerization method referred to here is a polymerization initiator and a surfactant in an aqueous medium, and (a) alkyl acrylate and / or methacrylic acid alkyl ester as monomer units (b) radicals. A polymerizable unsaturated carboxylic acid monomer and, if desired, (c) at least one monomer selected from a diene compound, an aromatic vinyl compound and a vinyl cyan compound are charged, premixed with a homogenizer. This is a method in which the particle size of oil droplets is adjusted by homogenization treatment and the temperature is raised to a predetermined temperature to carry out a polymerization reaction. An oil-soluble radical initiator is used as the polymerization initiator. Examples thereof include hydroperoxides such as cumene hydroperoxide, t-butyl isopropylbenzene hydroperoxide, t-butyl hydroperoxide and isopropyl hydroperoxide, dibenzoyl peroxide, diacyl peroxides such as dilauroyl peroxide, diisopropyl peroxydicarbonate, di- 2-
Peroxydicarbonates such as ethylhexyl peroxydicarbonate Peroxyesters such as t-butylperoxypivalate and t-butylperoxyneodecanoate 2,2′-azobisisobutyronitrile, 2,2′-
Examples thereof include azo compounds such as azobisdimethylvaleronitrile. These may be used alone or in combination of two or more, and the amount used is usually selected in the range of 0.001 to 5 parts by weight per 100 parts by weight of the monomer used.

As the surfactant, nonionic and cationic surfactants are mainly used, mainly anionic surfactants. Examples of the anionic surfactant, sodium lauryl sulfate, alkyl sulfate salts such as sodium myristyl sulfate, sodium dodecylbenzenesulfonate, alkylarylsulfonates such as potassium dodecylbenzenesulfonate, sodium dioctylsulfosuccinate, In addition to sulfosuccinate ester salts such as sodium dihexyl sulfosuccinate, fatty acid salts such as ammonium laurate and potassium stearate, polyoxyethylene alkyl sulfate ester salts, polyoxyethylene alkylaryl sulfate ester salts and the like can be mentioned. Examples of the nonionic surfactants include compounds having a polyoxyethylene chain in the molecule and having a surfactant activity, such as polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl ethers, and polyoxyethylene alkyl esters. And compounds in which the polyoxyethylene chain of the compound is replaced by a copolymer of oxyethylene and oxypropylene, sorbitan esters, glycerin alkyl esters, and the like. Further, examples of the cationic surfactant include cetylpyridinium chloride,
Cetyl trimethyl ammonium bromide etc. are mentioned. These may be used alone or in combination of two or more.
It is selected in the range of 0.05 to 5 parts by weight, preferably 0.2 to 4 parts by weight, per 00 parts by weight.

In this fine suspension polymerization, usually 30 to
Polymerization is carried out at a temperature in the range of 80 ° C. to obtain a latex of resin particles having an average primary particle size of 0.5 to 3 μm and a wide particle size distribution. This latex is usually subjected to a known treatment such as spray drying, and the polymer is taken out as a solid. The molecular weight of the polymer is appropriately adjusted by the reaction temperature and the molecular weight modifier according to the purpose.

The emulsion polymerization method is a method in which each monomer is copolymerized in an aqueous medium containing an emulsifier and a water-soluble polymerization initiator. As the emulsifier, the same one as the surfactant in the fine suspension polymerization method is usually used by using the anionic surfactant alone or in combination with the nonionic surfactant. These may be used alone or in combination of two or more. In addition, the amount of the anionic surfactant and nonionic surfactant used is 100
It is selected in the range of 0.1 to 5 parts by weight per part by weight.

On the other hand, as the polymerization initiator, a water-soluble inorganic peroxide or a combination of a water-soluble reducing agent and an organic peroxide is used. Examples of water-soluble inorganic peroxides include potassium persulfate and ammonium persulfate. As an example of the water-soluble reducing agent, a reducing agent used as an ordinary radical redox polymerization catalyst component soluble in water, for example, ethylenediaminetetraacetic acid or its sodium salt or potassium salt, or iron, copper, chromium, etc. Complex compound with heavy metal, sulfinic acid or its sodium salt or potassium salt, L-ascorbic acid or its sodium salt, potassium salt, calcium salt, ferrous pyrophosphate, ferrous sulfate, ferrous ammonium sulfate, sodium sulfite , Acidic sodium sulfite, sodium formaldehyde sulfoxylate, reducing sugars and the like. These may be used alone or in combination of two or more, and the amount thereof used is usually selected in the range of 0.0001 to 5 parts by weight per 100 parts by weight of the monomer used. As the organic peroxide, the same one as the hydroperoxide type radical initiator in the fine suspension polymerization is used. These may be used alone or in combination of two or more, and the amount used is usually selected in the range of 0.001 to 5 parts by weight per 100 parts by weight of the monomer used.

In this emulsion polymerization, higher fatty acids, higher alcohols, inorganic salts, water-soluble polymer compounds and the like may be used in combination in order to promote the action of the emulsifier and the polymerization catalyst used.

In this emulsion polymerization, usually 30 to 80
Polymerization is carried out at a temperature in the range of ℃, the particle size is 0.0
A latex in which copolymer fine particles of about 3 to 0.7 μm are uniformly dispersed is obtained. This latex is usually subjected to a known treatment such as salting out or spray drying, and the copolymer is taken out as a solid. The molecular weight of the copolymer is appropriately adjusted by the reaction temperature and the molecular weight modifier according to the purpose.

In the seeded emulsion polymerization method, the resin particles prepared by the above emulsion polymerization method are used as cores, and the same emulsifier and polymerization initiator as those used in the above emulsion polymerization method are used. It is a method of making. The diameter of the core particles is usually in the range of 0.03 to 0.7 μm on average, and the amount thereof is usually 1 to 5 per 100 parts by weight of the monomer used.
It is selected in the range of 0 parts by weight. The types and amounts of the emulsifier and the polymerization initiator are the same as those in the emulsion polymerization method. Further, as in the case of emulsion polymerization, higher fatty acids, higher alcohols, inorganic salts, water-soluble polymer compounds and the like may be used in combination in order to promote the action of the emulsifier and the polymerization catalyst used.

Next, a preferred example of the seed emulsion polymerization method will be described. First, an aqueous emulsion of desired resin core particles is prepared, then the water-soluble reducing agent and the monomer are charged therein, and the mixture is heated and maintained at a temperature of about 30 to 80 ° C.
On the other hand, an aqueous emulsion of organic peroxide and an aqueous solution of the emulsifier are separately prepared by using the emulsifier, and these are usually added to an aqueous emulsion containing the resin core particles, a water-soluble reducing agent and a monomer. Continuously charging while maintaining a temperature in the range of 30 to 80 ° C., a polymerization reaction is performed, and the obtained emulsion containing particles having an average particle size of 0.3 to 2 μm is treated in the same manner as in emulsion polymerization. The copolymer is taken out as a solid. The molecular weight of this copolymer is appropriately adjusted by the reaction temperature, the molecular weight modifier and the like depending on the purpose.

In the present invention, the ionic crosslinked product constituting the particles of the component (A) is prepared by adding a monovalent metal cation (A-2) to the above copolymer (A-1) to give the copolymer (A-1). It is a product obtained by ionically crosslinking the carboxyl groups present in the united body.
The cation used here is not particularly limited, and examples thereof include potassium cation, sodium cation, magnesium cation, calcium cation, barium cation, iron cation, nickel cation, copper cation, zinc cation, cesium cation, tin cation, and chromium cation. , Lead cations, strontium cations, aluminum cations and the like. These may be used alone or in combination of two or more. Among these, especially potassium cation, zinc cation,
The calcium cation is preferred.

In the ionic crosslinked product according to the present invention, unlike the crosslinked structure of covalent bond such as sulfur crosslinked or peroxide crosslinked, the formation of the crosslinked structure is thermoreversibly changed. for that reason,
The surface of the resin particles modified by ionic crosslinking exhibits the properties of a crosslinked structure at room temperature and the properties of a structure in which the crosslinking is dissociated under the processing conditions of heat molding. Further, since the three-dimensional polymer structure is formed in the outer shell layer of the particles, the swelling of the resin (A) due to the dispersion medium in the plastisol at room temperature is suppressed. This makes it possible to suppress the change in the viscosity of plastisol with time without impairing the original physical properties of the heat-processed product, resulting in improved storage stability. Therefore, by using the ionic crosslinked product as a resin component, a plastisol composition having both storage stability and moldability can be obtained.

The ionic crosslinked product according to the present invention can be produced by adding the monovalent metal cation (A-2) to the above copolymer (A-1). The metal cation may be added directly or in the form of a solution such as an aqueous solution. As the addition form, oxides, hydroxides, phosphates of trivalent metal cations,
Carbonates, nitrates, sulphates, chlorides, nitrites, sulphites and 10-octylic acid, stearic acid, oleic acid, capric acid, formic acid, succinic acid, erucic acid, linolenic acid, palmitic acid, propionic acid, acetic acid, adipine It can be in the form of salts of organic acids such as acids, butyric acid, naphthenic acid and thiocarboxylic acid, 11 acetylacetone salts, 12 ethoxide and methoxide alcoholates. Of these, monovalent metal hydroxides and carboxylates are preferably used from the viewpoint of reaction efficiency in crosslinking and ease of deformation during heat molding.

The ionic crosslinked product according to the present invention is one in which some or all of the free carboxyl groups are ionized to form a carboxyl anion, and an ionic bond is formed using a monovalent metal ion as a counter cation. Therefore, the ionic crosslinking rate can be easily adjusted by the amount of the metal cation supplier added. The above-mentioned ionic crosslinking reaction generally proceeds quantitatively, but an excess of the theoretical amount of the monovalent metal cation or its metal cation supplier can be used. The presence of this ionic cross-link can be easily analyzed by measuring the absorption of the carboxylate group by infrared absorption spectrum, quantifying the metal ion, and measuring the degree of swelling in the solvent. The dissociation property of ionic crosslinks can be confirmed by differential thermal analysis, and the density can be confirmed by measuring the degree of swelling.

When the copolymer (A-1) according to the present invention is polymerized by copolymerizing a radical-polymerizable unsaturated carboxylic acid in an aqueous polymerization solution, the carboxylic acid is hydrophilic. Most of them are accumulated on the surface layer of the fine particles. Therefore, when the metal cation supplier is added to the aqueous layer, the probability of encountering the metal cation dissociated in the aqueous layer with the highly dissociative carboxylic acid is extremely high because it is a reaction between ions. The ionic crosslinking reaction can be carried out in a short time. Further, the temperature dependence of the ionic crosslinking rate of the copolymer fine particles is small, and the amount of metal ions present in the copolymer after ionic crosslinking remains unchanged in the temperature range of 0 to 50 ° C.
Therefore, in the ionic crosslinking reaction, constant ionic crosslinking can be easily obtained without particularly controlling the temperature.

In order to efficiently obtain the ionic crosslinked product according to the present invention, a metal cation having a valence of 1 to 3 per free carboxyl group contained in the copolymer or a cation thereof, depending on the desired degree of crosslinking, is obtained. It is necessary to choose the molar ratio of metal atoms in the feed. The addition amount of the metal cation or the supplier thereof is
The preferable range is 0.02 to 2 times by mole, and the most preferable range is 0.05 to 1 times by mole with respect to the amount of carboxylic acid in the copolymer. By selecting these molar ratios, a plastisol composition having excellent storage stability and mechanical properties particularly in a sheet state can be obtained by using the ionic crosslinked product of the present invention. When the above molar ratio is less than 0.02, a large amount of free carboxyl groups remain, so that ionic crosslinking is difficult to be performed. Therefore, the storage stability of the plastisol composition is not improved. Further, the sheet using the plastisol composition has poor rust resistance and cannot be put to practical use. On the other hand, if the amount exceeds 2 times the molar amount, a large amount of hydroxyl groups remain, and the water resistance of the sheet using the plastisol composition deteriorates.
Mechanical properties tend to deteriorate. From the viewpoint of water resistance, the amount of carboxyl groups in the ionic crosslinked product that are not involved in ionic crosslinking is preferably 1% by weight or less based on the total weight of the copolymer.

The following methods are mentioned as specific examples of the method for obtaining the ionic crosslinked product according to the present invention. For example, a method of dissolving the copolymer (A-1) in a suitable solvent and adding a solution such as the metal cation or the metal cation supplier or an aqueous solution thereof to the polymer solution to cause an ionic crosslinking reaction. Method of adding the metal cation or a solution such as a metal cation supplier or an aqueous solution thereof to the latex after the polymerization step of the polymer (A-1) Plastisol by adding the powder of the copolymer (A-1) to the dispersion medium. A method of adding the metal cation or the metal cation supplier in the process of mixing and adjusting the above. Any of these methods can be used as a method for obtaining the ionic crosslinked product according to the present invention, but from the viewpoint of dispersion efficiency and handleability, the latex addition method is very simple and useful.

As the resin of the component (A) of the present invention, an ionic crosslinked product obtained by ionically crosslinking the whole particle with a copolymer containing a free carboxyl group can be used, or only the outer shell layer of the particle is ionically crosslinked. It is also possible to use an ionic crosslinked product.

The resin as the component (A) of the present invention can be produced by granulating the ionically crosslinked product. Particle formation is carried out by various known methods, for example, by adding a metal cation supplier or an aqueous solution thereof to the above copolymer dispersion obtained by copolymerization for ionic crosslinking, and then drying it by a spray drying method or the like. It can be done by things. The particle size is not particularly limited and is usually in the range of 0.03 to 5 μm in terms of average primary particle size.

In the foamable plastisol composition of the present invention, the epoxy resin used as the component (B) has one or more epoxy groups in the molecule. Examples of such products include bisphenol A, bisphenol F, resorcin,
Diglycidyl ether such as hydrogenated bisphenol A,
Examples include glycidyl ether type such as polyglycidyl ether of phenol novolac resin and cresol novolac resin, glycidyl ester type such as phthalic acid, hexahydrophthalic acid, tetrahydrophthalic acid, glycidyl amine type, and linear aliphatic epoxide type. These epoxy resins can be used alone or in combination depending on the properties required for the foam.

Regarding the mixing ratio of the epoxy resin of component (B) and the resin of component (A), the ratio of component (A) / (B)
It is necessary that the component weight ratio is within the range of 0.1 to 5, preferably 0.3 to 2. If the weight ratio is less than 0.1, it is not possible to obtain a foam having high toughness and a dense and uniform surface, and if it exceeds 5 the viscosity of the plastisol increases, and high-speed coating processing in sheet production is required. It will be difficult.

The plasticizer used as the component (C) in the expandable plastisol composition of the present invention has a function of stably mixing and dispersing the acrylic resin of the component (A) in the epoxy resin of the component (B). At the same time, it has a role of adjusting the melt viscosity of the plastisol. Examples of the plasticizer include phthalic acid esters such as 2-ethylhexyl phthalate and dibutyl phthalate, phosphoric acid esters such as tricresyl phosphate, fatty acid esters such as dioctyl adipate and dioctyl sebacate, ethylene glycol and adipic acid. Examples include conventionally known ones such as polyesters such as condensation products with, trimellitic acid triesters such as trioctyl trimellitate, chlorinated paraffins, alkylbenzenes, and high molecular weight aromatics. Even if only one of these is used, 2
You may use it in combination of 2 or more types. Among these,
Phthalates such as 2-ethylhexyl phthalate are preferred.

The amount of the plasticizer blended is not particularly limited, but is usually 20 to 100 parts by weight of the component (A).
It is selected in the range of 150 parts by weight. Below 20 parts by weight,
It is not possible to obtain a foam having high toughness and a dense and uniform surface, and when it exceeds 150 parts by weight, the rigidity as a reinforcing material is significantly reduced.

Examples of the high temperature decomposition type foaming agent used as the component (D) in the foamable plastisol composition of the present invention include organic foaming agents, inorganic foaming agents and high temperature expansion type microcapsules. Examples of organic foaming agents include azodicarbonamide, p-toluenesulfonyl hydrazide, dinitrosopentamethylenetetramine, 4,
4'-oxybisbenzenesulfonyl hydrazide and the like can be mentioned. The decomposition temperature of these organic blowing agents is urea,
It can be arbitrarily adjusted by adding a zinc compound, a lead compound or the like. Examples of the inorganic foaming agent include sodium hydrogen carbonate, sodium borohydride, and the like, and examples of the high temperature expansion type microcapsules include:
For example, a vinylidene chloride resin in which a low boiling point hydrocarbon is encapsulated may be used.

In the present invention, any of the above-mentioned organic foaming agents, inorganic foaming agents and high temperature expansion type microcapsules can be used, but it is easy to form a sheet, the appearance of the foam, the uniformity of foaming and the denseness. The decomposition temperature is 1
An organic foaming agent having a temperature of 20 ° C. or higher is suitable. Decomposition temperature is 12
If the temperature is lower than 0 ° C, foaming may start at the time of sheet formation. In addition, since the resin melts insufficiently during foaming in a heating furnace and gas escapes, the expansion ratio does not increase,
It becomes difficult to obtain a homogeneous foam.

The blending amount of this foaming agent is usually 0.1 to 1 per 100 parts by weight, based on the sum of the components (A), (B) and (C).
It is selected in the range of 0 parts by weight. If it is less than 0.1 part by weight, the expansion ratio is low, the rigidity is the same at the same surface weight, and the thermal conductivity is also significantly reduced. On the other hand, when the amount exceeds 10 parts by weight, the cells of the foam layer become coarse, and when applied as a reinforcing sheet to a vertical portion or a flat portion of a vehicle outer panel, the cells fall off or shift from the panel immediately after heating.

As the heat-activatable curing agent for the epoxy resin used as the component (E) in the expandable plastisol composition of the present invention, a usual curing agent exhibiting a curing action by heating is used. As the curing agent, one having a curing temperature in the range of 120 to 200 ° C. in combination with an epoxy resin is preferable. Examples thereof include dicyandiamide, 4,4′-diaminodiphenyl sulfone, 2-n
Imidazole derivatives such as heptadecyl imidazole, isophthalic dihydrazide, N, N-dialkylurea derivatives, N, N-dialkylthiourea derivatives, acid anhydrides such as tetrahydrophthalic anhydride, isophoronediamine, m-phenylenediamine, Examples thereof include N-aminoethylpiperazine, boron trifluoride complex compound, and trisdimethylaminomethylphenol. The curing temperature here means the temperature of the medium at which the heat generated by curing reaches a peak when a mixture of an epoxy resin and a curing agent at room temperature is heated by an oil bath, a heater, or the like. Further, the preferable combination and amount of the epoxy resin and the curing agent depending on the heating conditions can be easily determined by conducting a test in advance.

These curing agents may be used alone or in combination of two or more. The blending amount is usually selected in the range of 3 to 30 parts by weight per 100 parts by weight of the epoxy resin. If the amount is less than 3 parts by weight, the curing will be insufficient and the rigidity of the reinforcing material using the foam will be insufficient. Meanwhile, 30
When it exceeds the weight part, partial decomposition or thermal deterioration occurs due to excessive exothermic reaction during molding, the rigidity of the foam does not improve relative to the amount used, and it is rather economically disadvantageous.

In the present invention, together with the curing agent of the component (E), if desired, as a curing accelerator, for example, alcohol type, phenol type, mercaptan type, dimethylurea type, alicyclic type, and further imidazole, Monuron, chlorotoluron, etc. can be used.

The foamable plastisol composition of the present invention comprises:
In addition to the above essential components, a foaming aid, a colorant, and a filler such as calcium carbonate, talc, or clay can be used, if desired. Regarding the blending amount of these components, the filler is usually 5 to 100 parts by weight of the component (A).
200 parts by weight and the foaming aid are selected in the range of 0.1 to 4 parts by weight. If the blending amount of the filler exceeds 200 parts by weight, the expansion ratio cannot be increased and the fineness of the foaming itself is lost. Further, even if the amount of the foaming auxiliary compounded is more than 4 parts by weight, the effect is not improved for the amount.

The expandable plastisol composition of the present invention comprises the above-mentioned components (A), (B), (C), (D),
It can be prepared by kneading the component (E) and various additive components used as necessary in predetermined amounts with a known kneader such as a planetary mixer, a kneader, a roll or a Henschel mixer.

The sheet material for panel reinforcement of the present invention has a two-layer structure in which the first layer made of the expandable plastisol composition prepared as described above and the second layer made of fiber cloth are laminated. And a first layer, a second layer, and a third layer composed of a metal thin film having a thickness of 100 μm or less, which are laminated to form a three-layer structure.

In the sheet material for panel reinforcement of the present invention, the fiber cloth used for the second layer is not particularly limited, and may be, for example, woven organic or inorganic fiber,
Alternatively, any of mesh-like, cloth-like, film-like, and mat-like ones obtained by binding short fibers with a binder can be used, but it is desirable to use a material having durability in the heating step. Further, the thickness is preferably 1 mm or less.
It is difficult to obtain a smooth surface with a material that is deformed or shrunk in the heating step. On the other hand, if the thickness exceeds 1 mm, the weight and bulk of the entire sheet increase, and the workability deteriorates. Examples of heat resistant fibers include fibers of polyester, nylon, polyamide, carbon, glass, metal and the like. Among them, glass fiber is preferably used in terms of workability and performance.

In the sheet material for panel reinforcement of the present invention, the metal thin film used for the third layer is a planar base material which supports the expandable plastisol composition. This facilitates application, transport, application of the composition to metal panels, etc.
At the same time as improving the workability, it gives the function of improving the surface strength and barrier properties of the foamed panel.
It is desirable to have characteristics such as being rigid and non-stretchable, being flexible and lightweight. As such, a metal foil having a thickness of 100 μm or less, such as aluminum, stainless steel, zinc, tin, nickel, copper,
A foil such as iron is used. Among them, the aluminum foil is the most excellent in terms of economical efficiency as well as malleability. If the thickness exceeds 100 μm, not only the weight increases but also the flexibility decreases, so that when it is attached to a panel having a curved surface, it does not conform to the shape and it is difficult to obtain a foam having a uniform wall thickness.

An example of the method for producing the panel reinforcing sheet material of the present invention is shown below. (1) The foamable plastisol composition is directly applied to the cloth cloth or the cloth cloth on which the fiber cloth and the metal thin film are laminated in advance, and the mixture is heat-molded at a temperature lower than the decomposition temperature of the foaming agent. How to solidify. (2) The foamable plastisol composition is continuously heat-molded on a release paper or steel belt at a temperature lower than the decomposition temperature of the foaming agent to form a sheet, and then a fiber cloth or a fiber cloth is formed thereon. Method of laminating cloth and metal thin film. Of these, the method (1) is preferable, and a release paper may be provided on the surface of the foamable composition layer, if desired. The panel reinforcing sheet material obtained by the above method is flexible and rich in elasticity, and is easy to wind, cut and carry.

In the sheet material for reinforcing a panel of the present invention, the foamable plastisol composition layer (first layer) surface exhibits self-adhesiveness, and is applied to the back surface of the outer panel without any adhesive treatment or adhesive. Can be easily attached simply by pressing. This is because the epoxy resin of component (B) is absorbed by the ionically crosslinked resin of component (A) in the process of forming a molded sheet, but the epoxy resin that cannot be absorbed remains in the sheet, and It is thought that this is because it exhibits tackiness. Although such a phenomenon was not expected at all at first, it was discovered by chance in the process of searching for sheeting conditions, and it can be said that the present invention is practically excellent and epoch-making. . Of course, in order to further increase the tackiness, it is possible to additionally add a tackifier other than the epoxy resin to the foamable composition, and the adhesive is applied to the surface of the molded sheet or the outer panel. It is also possible. In any case, compared to the conventional method of pasting a foamed molded product or a heat insulating material such as felt using an adhesive or an adhesive,
A thin and flexible sheet can be applied very easily by simply crimping it, and moreover, it can be evenly attached over the entire surface according to the shape of the outer panel.

When the sheet material for panel reinforcement of the present invention is heat-processed, a foamed layer having a high closed cell rate is formed.
When a particularly high degree of rust prevention is required, a plastisol composition obtained by removing only the component (D) of the expandable plastisol composition of the present invention on the surface directly attached to the outer panel is 400 μm or less. It is effective to stack them with a thickness and combine thin non-foamed layers.

In this way, the reinforcing sheet material attached so that the foamable plastisol composition layer (first layer) is in contact with the back surface of the outer panel is 180 to 22 in a heating furnace or the like.
By heating at a temperature of about 0 ° C., foaming and curing are performed, and an outer panel structure having improved heat insulation and strength can be obtained.

The mechanism of foaming and curing is considered as follows, taking the case of using an organic foaming agent as an example.
That is, first, the ion-crosslinked resin of the component (A) of the first layer (foamable plastisol composition layer) is melted by heating, and then the foaming agent is decomposed to generate gas. The evolved gas causes the system to foam and form cells which are subsequently included in the composition,
The dispersed epoxy resin causes a curing reaction due to activation of the curing agent, and the foam becomes hard. Therefore, the characteristics of the foam to be formed are influenced by the gelation rate of the component (A), the decomposition rate of the foaming agent, and the curing rate of the epoxy resin. Therefore, the material is selected based on the target foaming density and curing degree. There is a need to.

It is most rational to use an existing electrodeposition coating furnace as a heating furnace to be used when heating after being attached to the inner surface of the vehicle outer panel, and it is not necessary to provide a separate baking furnace. Absent.

The sheet material for panel reinforcement obtained in the present invention is excellent in oil surface tackiness, and the foamed and hardened sheet has good heat resistance, heat insulation and rigidity. It is preferably used to reinforce.

[0067]

EXAMPLES The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto. The viscosity of the plastisol, the oil surface tackiness of the unfoamed sheet, and the properties of the steel sheet / resin composite were evaluated as follows. (1) Viscosity of plastisol Using a Brookfield rotary viscometer at a temperature of 25 ° C,
The measurement was performed under the condition of relative humidity of 60%. Plastisol was stored at 40 ° C for 7 days and the temperature was 25 ° C and the humidity was 60 ° C.
% Is an index value obtained by dividing the viscosity measured by placing it for 1 hour by the viscosity of the first day.

(2) Oil surface tackiness The unfoamed tacky sheet after heating at 110 ° C. for 3 minutes was pressure-bonded to a steel plate at room temperature for 3 kg for 10 seconds to obtain 180 samples.
The peel strength was determined and the oil surface tackiness was evaluated. (3) 1 mm displacement bending rigidity The load (kgf) when deformed by 1 mm was obtained by the method shown in FIG. In FIG. 1, 1 is a steel plate, 2 is a foam-hardened sheet, 3 is a glass cloth, and the unit of numerical value is mm. (4) Maximum load bending displacement By the method shown in FIG. 1, the bending displacement (mm) when the sample yielded under load was determined. (5) Foaming ratio This is a value obtained by dividing the thickness of the foamed layer cross section by the thickness of the foamable composition layer in the unfoamed stage. Also used steel plate (0.8 mm thickness)
The 1 mm displacement bending rigidity was 1.0 kgf, and the maximum load bending displacement was 26 mm. (6) Cell state The surface state of the foam layer was visually observed.

Example 1 The following monomers and polymerization agents were charged into a 10-liter stainless steel premixing vessel having a two-stage stirring blade and mixed at 30 ° C. for 1 hour. Monomer / Polymerization Agent Weight Part Methyl Methacrylate 85 Ethyl Acrylate 13 Methacrylic Acid 2 Linear Higher Alcohol (C18) 2 Sodium Alkylbenzene Sulfonate 0.5 Styrene 65 Benzoyl Peroxide 0.3 Distilled Water 200

After mixing, the suspension formed by stirring was passed once through a two-stage pressure homogenizer, the first and second stages of which were 1200 psi each, and then 10 liters with a two-stage stirring blade. The mixture was transferred into a pressure vessel made of stainless steel, fine suspension polymerization was carried out at 75 ° C., and the polymerization was stopped when the polymerization conversion rate reached 95%.

0.4 parts of potassium hydroxide as a metal cation supplier was added to and mixed with the latex obtained by the polymerization, and the mixture was stirred at 23 ° C. for 10 minutes to obtain a latex. Next, this was spray-dried in a nitrogen gas stream at 170 ° C. to produce resin particles composed of an ion-crosslinked product having an average primary particle size of 1 to 2 μm.

Next, the resin particles and the following chemicals were put into a vacuum degassing planetary mixer all at once and mixed for 20 minutes to prepare a plastisol composition. Blend composition Ion-crosslinked product particles 100 Bisphenol A type liquid epoxy resin 200 2-Ethylhexyl phthalate 80 Curing agent ¹⁾ 20 Curing accelerator ²⁾ 4.5 Organic foaming agent ³⁾ 3 Foaming aid ⁴⁾ 2 Filler ⁵⁾ 100 Note 1) Dicyandiamide (manufactured by Nippon Carbide Co., Ltd.) * 2) DP Hardener (manufactured by Maruwa Biochemical Co., Ltd.) * 3) AZ-H (manufactured by Otsuka Chemical Co., Ltd.) * 4) FL-23 (Asahi) Denka Kogyo Co., Ltd.) Note 5) Whiten H (Shiraishi Kogyo Co., Ltd.)

This plastisol had good storage stability and a viscosity that could be easily coated and processed for a long period of time. In consideration of processability and handleability, it is preferable that the time-dependent change index of sol viscosity for 7 days is 1.5 or less.

The plastisol thus obtained is
An unfoamed adhesive sheet (sheet material for panel reinforcement) was applied to a glass cloth having a thickness of 300 μm with a knife coater to a thickness of 1.0 mm and heated in a hot air circulation oven at 110 ° C. for 3 minutes. It was prepared and its oil surface tackiness was determined.

Next, this unfoamed adhesive sheet was made to have a thickness of 0.
A steel plate / resin composite sample provided with a hard foam sheet with a glass cloth, which was adhered to an 8 mm oil surface steel plate by applying pressure of 3 kg for 10 seconds and then heated in a hot air circulation oven at 180 ° C. for 30 minutes. Was prepared and its characteristics were determined. The sizes of the steel plate and the non-foaming adhesive sheet are both 150 × 25 mm. The results are shown in Table 1.

Examples 2 to 6 Ion-crosslinked resin particles were obtained in the same manner as in Example 1 except that the types of polymerizable monomer components shown in Table 1 were used. Same as 1. The results are shown in Table 1.

Example 7 Ion-crosslinked resin particles were obtained in the same manner as in Example 1 except that zinc acetate was used as the metal cation supplier, and the operations and evaluations after the preparation of the sol were performed in the same manner as in Example 1. . The results are shown in Table 1.

Example 8 Ion-crosslinked resin particles were obtained in the same manner as in Example 1 except that polymerized monomer components of the types shown in Table 1 and aluminum hydroxide as a metal cation supplier were used to prepare a sol. The subsequent operations and evaluations were the same as in Example 1. The results are shown in Table 1.

Example 9 The same polymerization as in Example 1 was carried out, followed by spray drying without adding a metal cation supplier, and the average primary particle size was 2 μm.
Resin particles of Example 1 except that these particles were used
In the same manner as above, operations and evaluations after the preparation of the sol were performed. The results are shown in Table 1.

Comparative Example 1 Polymerization was carried out under the same conditions as in Example 1, using only methyl methacrylate as the polymerizing monomer component. Then, spray drying was performed without adding a metal cation supplier to obtain resin particles. Operations and evaluations after the preparation of the sol were carried out in the same manner as in Example 1 except that these particles were used. However, after the unfoamed adhesive sheet was attached to the oil surface steel plate, heating in a hot air circulation furnace was performed at 150 ° C. The results are shown in Table 1.

Comparative Examples 2 to 5 Polymerization was carried out under the same conditions as in Example 1, using the polymerizable monomer components shown in Table 1. Then, spray drying was performed without adding a metal cation supplier to obtain resin particles. Operations and evaluations after the preparation of the sol were carried out in the same manner as in Example 1 except that these particles were used. The results are shown in Table 1.

[0082]

[Table 1]

As can be seen from Table 1, the panel-reinforcing sheet material produced by processing the plastisol composition of the present invention having good storage stability has excellent oil surface tackiness, and
The obtained steel plate / resin composite has good displacement rigidity of 1 mm, maximum bending displacement, thermal conductivity, expansion ratio, and cell state.

[0084]

EFFECT OF THE INVENTION The sheet material for reinforcing a panel of the present invention is excellent in oil surface tackiness and can be easily adhered to an outer panel without using an adhesive treatment or an adhesive. Since it is excellent in heat insulation and rigidity and also excellent in heat resistance, it is particularly suitable for reinforcement of vehicle outer panel before electrodeposition coating, unlike conventional ones based on vinyl chloride resin. Further, since the plastisol composition used for the sheet material for reinforcing a panel of the present invention has excellent storage stability, its productivity can be remarkably improved without impairing the characteristics as a sheet material.
By applying the reinforcing sheet material of the present invention to a vehicle outer panel before electrodeposition coating, the use area is expanded and foaming and curing can be performed by utilizing the heating during electrodeposition coating, so that production in an automobile production line is possible. The property is improved. The vehicle exterior panel structure of the present invention produced by using the panel reinforcing sheet material is characterized by being lightweight and excellent in heat insulating property, rigidity and heat resistance.

[0085]

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a method for measuring a 1 mm displacement bending rigidity and a maximum load bending displacement of a steel plate / resin composite sample.

[0086]

[Explanation of symbols]

 1 Steel plate 2 Foam hardening sheet 3 Glass cloth

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location C08L 63/00 NJP 8830-4J (72) Inventor Seiki Yada 1-chome Yokko, Kawasaki-ku, Kanagawa Prefecture 2-1 Japan Zeon Co., Ltd. Research and Development Center

Claims (4)

[Claims] 1. An acrylic resin comprising (A) (a) an alkyl acrylate and / or methacrylic acid alkyl ester and (b) a radical-polymerizable unsaturated carboxylic acid monomer, and having (a) as a main constituent unit. Resin obtained by adding a monovalent metal cation (A-2) to the copolymer (A-1), (B) epoxy resin, (C) plasticizer, (D) high temperature decomposition type foaming agent And (E) a sheet material for panel reinforcement having a structure in which a first layer made of a plastisol composition containing a heat-activatable curing agent for an epoxy resin as an essential component and a second layer made of a fiber cloth are laminated. 2. An acrylic resin comprising (A) (a) an alkyl acrylate and / or methacrylic acid alkyl ester and (b) a radical-polymerizable unsaturated carboxylic acid monomer, and having (a) as a main constituent unit. Resin prepared by adding a monovalent metal cation (A-2) to the copolymer (A-1), (B) epoxy resin, (C) plasticizer, (D) high temperature decomposable foaming agent And (E) a first layer composed of a plastisol composition containing a heat-activatable curing agent for epoxy resin as an essential component, a second layer composed of a fiber cloth, and a third layer composed of a metal thin film having a thickness of 100 μm or less. A sheet material for panel reinforcement having a laminated structure. 3. The method according to claim 1, wherein at least one monomer (c) selected from a diene compound, an aromatic vinyl compound and a vinylcyan compound is used as an acrylic copolymer (A-1) component. The sheet material for reinforcing a panel as described above. 4. A panel reinforcing sheet material according to any one of claims 1 to 3 is provided on a rear surface of a vehicle outer panel so that the first layer surface of the sheet material is in contact with the foamed material. , A vehicle outer panel structure formed by curing.