JP5691675B2 - Method for producing foamed film - Google Patents

Description

  The present invention relates to a foam film composition and a method for producing a foam film using the composition.

  For the purpose of improving thermal insulation and sound absorption properties, the technology of coating metal or building materials with resin foam, rubber foam, rock wool, glass wool, etc. is generally widely used as a method for improving thermal efficiency and preventing noise. ing. However, in such a conventional coating technique, there is a problem that it is extremely difficult to construct a complicated part of the surface shape. Therefore, the following technique is proposed to solve such a problem. ing.

Patent Document 1 proposes the use of a heat-insulating paint composed of ceramic hollow particles and an adhesive resin emulsion.
Patent Document 2 discloses that a foamable paint containing a polyol compound, an isocyanate compound and water is used to produce a polyurethane resin by the reaction of the polyol compound and the isocyanate compound, and at the same time, a dioxide dioxide produced by the reaction of the isocyanate compound and water. It has been proposed to form voids in the paint film with carbon.
Furthermore, Patent Document 3 proposes a foamable coating composition containing a specific modified polyol, a blocked isocyanate, and an amide-based foaming agent.

However, when ceramic hollow particles are blended, the dispersion state of the hollow particles in the foamed film becomes non-uniform due to the difference in specific gravity, which causes a problem that it is difficult to obtain a uniform foamed film.
Moreover, in the technique using the void formation by the carbon dioxide produced | generated by reaction with an isocyanate compound and water, it is difficult to control the production | generation conditions and there exists a problem that it is difficult to obtain a uniform foamed film.
Furthermore, in the foamable coating composition containing an amide-based foaming agent, the amide-based foaming agent is a technology that forms voids in the film by a gaseous decomposition product generated by thermal decomposition. In order to form the film, precise temperature control is required, so that it is difficult to use it easily.

JP 2000-290594 A JP 2003-292890 A Japanese Patent Laid-Open No. 2005-206736

  In view of the above-mentioned conventional technology, the present invention is a foam that can easily form a foam film without blending a foaming agent that is difficult to control foaming or hollow particles that are difficult to produce a uniform foam film by localization. It is an object of the present invention to provide a film composition and a method for producing a foamed film using the composition.

  As a result of diligent studies to solve the above problems, the present inventors have found that an alkali-soluble polymer obtained by polymerizing an ethylenically unsaturated carboxylic acid and other monomers copolymerizable therewith with ammonia. In the presence of 10 to 200 parts by weight of an alkali-soluble polymer neutralized product obtained by summing, using a foamed film composition comprising an aqueous polymer dispersion obtained by emulsion polymerization of 100 parts by weight of a monomer mixture, The present inventors have found that a uniform foamed film can be formed by heating a dry film obtained by drying the composition at a high temperature, thereby completing the present invention.

Thus, according to the present invention, in an alkali-soluble polymer obtained by neutralizing an alkali-soluble polymer obtained by polymerizing an ethylenically unsaturated carboxylic acid and other monomers copolymerizable therewith with ammonia. In the presence of 10 to 200 parts by weight of a Japanese product , a dry film obtained by drying a foam film composition comprising an aqueous polymer dispersion obtained by emulsion polymerization of 100 parts by weight of a monomer mixture is 180 ° C. or higher. There is provided a method for producing a foamed film, wherein the foamed film is heated and foamed.

  According to the present invention, a foamed film composition that can easily form a foamed film without blending a foaming agent that is difficult to control foaming or hollow particles that are difficult to produce a uniform foamed film by localization, and A method for producing a foamed film using the composition is provided.

  The foam film composition of the present invention comprises an alkali-soluble polymer obtained by neutralizing an alkali-soluble polymer obtained by polymerizing an ethylenically unsaturated carboxylic acid and other monomers copolymerizable therewith with ammonia. It consists of an aqueous polymer dispersion obtained by emulsion polymerization of 100 parts by weight of the monomer mixture in the presence of 10 to 200 parts by weight of the neutralized product.

  The alkali-soluble polymer used in the present invention is obtained by polymerizing an ethylenically unsaturated carboxylic acid and other monomers copolymerizable therewith.

  Examples of the ethylenically unsaturated carboxylic acid include ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; ethylenically unsaturated polyvalent carboxylic acids such as fumaric acid, maleic acid, itaconic acid, and butenetricarboxylic acid; Examples include partially esterified products of ethylenically unsaturated polyvalent carboxylic acids such as monoethyl maleate and monomethyl itaconate. Of these ethylenically unsaturated carboxylic acids, ethylenically unsaturated monocarboxylic acids such as (meth) acrylic acid are preferred.

The amount of the ethylenically unsaturated carboxylic acid is such that the acid value of the alkali-soluble polymer is usually in the range of 50 to 300, preferably 80 to 250. Usually, it is 5 to 50% by weight of the total monomer used to obtain the alkali-soluble polymer.
If the amount of ethylenically unsaturated carboxylic acid used is too small, the acid value of the alkali-soluble polymer will be small, and even if this alkali-soluble polymer is neutralized, it will be difficult to dissolve in water, so emulsification of the aqueous polymer dispersion The polymerization stability at the time of polymerization may decrease, and it may be difficult to stably obtain an aqueous polymer dispersion. Conversely, if the amount of ethylenically unsaturated carboxylic acid used is too large, the polymerization stability of the aqueous polymer dispersion during emulsion polymerization will decrease, making it difficult to stably obtain the aqueous polymer dispersion. There is a case.

  Other monomers copolymerizable with the ethylenically unsaturated carboxylic acid include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-amyl (meth) acrylate, ( Ethyl ethylenically unsaturated carboxylic acid alkyl ester monomers such as isoamyl acrylate, hexyl (meth) acrylate, ethyl hexyl (meth) acrylate, octyl (meth) acrylate; styrene, α-methylstyrene, vinyltoluene, Aromatic vinyl monomers such as chlorostyrene; hydroxyl-containing ethylenically unsaturated monomers such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; glycidyl (meth) acrylate and allyl glycidyl ether Glycidyl group-containing ethylenically unsaturated monomer; (meth) acrylonitrile, etc. Ano group-containing ethylenically unsaturated monomer; Amide group-containing ethylenically unsaturated monomer such as (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide; 1,3-butadiene Conjugated diene monomers such as isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene; vinyl halides such as vinyl chloride; and carboxylic acid vinyl esters such as vinyl acetate. These monomers can be used alone or in combination of two or more. Among these monomers, ethylenically unsaturated carboxylic acid alkyl esters such as methyl (meth) acrylate and ethyl (meth) acrylate are preferred because they are superior in polymerization stability during emulsion polymerization of an aqueous polymer dispersion. A mer is preferred.

  The alkali-soluble polymer used in the present invention has a weight average molecular weight of usually 1,000 to 20,000, preferably 2,000 to 15,000, more preferably 5,000 to 10,000. When the weight average molecular weight is too low, the polymerization stability of the aqueous polymer dispersion is lowered, and it may be difficult to stably obtain the aqueous polymer dispersion. On the other hand, if it is too high, the viscosity of the aqueous polymer dispersion may increase, and it may be difficult to handle.

  The alkali-soluble polymer used in the present invention has a glass transition temperature of usually 0 to + 200 ° C., preferably 0 to + 150 ° C.

  The alkali-soluble polymer is usually obtained by solution polymerization or emulsion polymerization, and preferably obtained by emulsion polymerization in the presence of a polymerizable surfactant.

  A polymerizable surfactant is a surfactant having one or more polymerizable carbon-carbon unsaturated bonds in the molecule. Specific examples include sodium propenyl-2-ethylhexylbenzenesulfosuccinate, sulfate of polyoxyethylene (meth) acrylate, ammonium polyoxyethylene alkylpropenyl ether sulfate, phosphate of (meth) acrylic polyoxyethylene ester Anionic polymerizable surfactants such as: Nonionic polymerizable surfactants such as polyoxyethylene alkylbenzene ether (meth) acrylic acid ester and polyoxyethylene alkyl ether (meth) acrylic acid ester. The amount of the polymerizable surfactant is usually 0.01 to 1.0 part by weight, preferably 0.05 to 0.8 part with respect to 100 parts by weight of all monomers used for the synthesis of the alkali-soluble polymer. Parts by weight. If the amount used is too small, it is difficult to emulsify the monomer, and the polymerization stability of the emulsion polymerization of the alkali-soluble polymer tends to decrease. On the other hand, if the amount is too large, the water resistance of the foamed film obtained using the aqueous polymer dispersion tends to decrease.

In the above polymerization, a polymerization initiator, a pH adjuster, a dispersant and the like that are usually used in emulsion polymerization can be appropriately selected and used.
Moreover, in order to adjust the weight average molecular weight of the alkali-soluble polymer, a molecular weight regulator usually used in emulsion polymerization can be appropriately selected and used.

The alkali-soluble polymer neutralized product is obtained by neutralizing the alkali-soluble polymer obtained as described above with ammonia. When neutralized with a basic substance other than ammonia, a foamed film cannot be obtained.
The degree of neutralization is preferably 70% or more, more preferably 90% or more, based on all carboxyl groups in the alkali-soluble polymer. If the degree of neutralization is too low, the alkali-soluble polymer neutralized product becomes difficult to dissolve in water, so that the polymerization stability during the emulsion polymerization of the aqueous polymer dispersion is lowered, and the aqueous polymer dispersion is stable. It may be difficult to obtain.

The aqueous polymer dispersion in the present invention is obtained by emulsion polymerization of 100 parts by weight of the monomer mixture in the presence of 10 to 200 parts by weight of the alkali-soluble polymer neutralized product.
As the monomer mixture, those appropriately selected from the monomers described below can be usually used.
A combination of an ethylenically unsaturated monomer containing a glycidyl group, an amide group or an amino group and a monomer copolymerizable therewith from the point of excellent adhesion to the adherend of the foam film. It is preferable to use it.

Examples of the ethylenically unsaturated monomer containing glycidyl group, amide group or amino group used in the monomer mixture include glycidyl group-containing ethylenically unsaturated monomers such as glycidyl (meth) acrylate and allyl glycidyl ether; Amide group-containing ethylenically unsaturated monomers such as (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide; dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate An amino group-containing ethylenically unsaturated monomer such as
The amount of these monomers is usually 0.5 to 15% by weight, preferably 1 to 10% by weight of the monomer mixture.

Monomers that can be copolymerized with an ethylenically unsaturated monomer containing a glycidyl group, an amide group or an amino group include cyano group-containing ethylenically unsaturated monomers such as (meth) acrylonitrile and β-cyanoethyl (meth) acrylate. Saturated monomer; Hydroxyl group-containing ethylenically unsaturated monomer such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; Pyridyl group-containing ethylenically unsaturated monomer such as 2-vinylpyridine; Styrene , Α-methylstyrene, vinyltoluene, chlorostyrene and other aromatic vinyl monomers; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-amyl (meth) acrylate, (Meth) acrylic acid isoamyl, (meth) acrylic acid hexyl, (meth) acrylic acid ethylhexyl, (meth) acrylic Ethylenically unsaturated carboxylic acid alkyl ester monomers such as octyl acid; conjugated diene monomers such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene; Examples thereof include vinyl halide monomers such as vinyl; carboxylic acid vinyl esters such as vinyl acetate.
Of these, ethylenically unsaturated carboxylic acid alkyl ester monomers, styrene and 1,3-butadiene are preferred. When 1,3-butadiene is used, it is within the range of 20 to 60% by weight of the monomer mixture. It is preferable to use it.

  The monomer mixture has a glass transition temperature of a copolymer obtained by polymerizing the monomer mixture, usually from −60 to + 150 ° C., preferably from −40 to + 100 ° C., and more preferably from −20 to 20 ° C. Adjust to + 60 ° C. If this glass transition temperature is too low, the shape retention of the resulting foamed film tends to be reduced. On the other hand, if it is too high, it tends to be difficult to obtain a homogeneous dried film before heating and foaming.

  The ratio between the neutralized alkali-soluble polymer and the monomer mixture is 10 to 200 parts by weight, preferably 20 to 150 parts by weight of the neutralized polymer of the alkali-soluble polymer with respect to 100 parts by weight of the monomer mixture. It is. If the amount of the alkali-soluble polymer neutralized product is too small, the polymerization stability in emulsion polymerization may be reduced, or the expansion ratio in the foamed film may be reduced. On the other hand, when the amount of the neutralized product is too large, it tends to be difficult to obtain a homogeneous dried film before heating and foaming.

As a method for emulsion polymerization of the monomer mixture in the presence of the alkali-soluble polymer neutralized product, the monomer mixture is added to an aqueous medium containing the neutralized product for polymerization, or the neutralized product is used. And the monomer mixture are mixed to form an emulsion, and then added to an aqueous medium or an aqueous medium containing the neutralized product for polymerization.
The polymerization temperature is usually 0 to 100 ° C, preferably 30 to 90 ° C.

  In the emulsion polymerization of the monomer mixture in the presence of the alkali-soluble polymer neutralized product, a surfactant can be used in combination in order to further increase the polymerization stability. The amount used is preferably 0.05% by weight or less, more preferably 0.02% by weight or less based on the monomer mixture so as not to impair the water resistance of the resulting foamed film.

In the above emulsion polymerization, polymerization auxiliary materials such as a polymerization initiator, a molecular weight adjusting agent, a pH adjusting agent, and a dispersing agent that are usually used in emulsion polymerization can be appropriately selected and used.
In addition, auxiliary materials such as pH adjusters, preservatives, antibacterial agents, and dispersants can be appropriately selected and added to the aqueous polymer dispersion after emulsion polymerization. Furthermore, you may perform the process of removing an unreacted monomer immediately after emulsion polymerization, or after adding a subsidiary material.

  The foamed film composition of the present invention comprises the aqueous polymer dispersion liquid obtained as described above. Although it can be used only with the above aqueous polymer dispersion, as long as the effect of the present invention is not substantially inhibited, a filler, a colorant, inorganic / organic hollow particles, inorganic / organic An appropriate amount of a foaming agent, a viscosity modifier, a leveling agent, an ultraviolet absorber, a light stabilizer, an antistatic agent, an antiblocking agent, an oxidation stabilizer, a plasticizer, and the like can also be blended.

The method for producing a foamed film according to the present invention is characterized in that the dried film obtained by drying the foamed film composition is heated at 180 ° C. or more to be foamed.
The foamed film composition is applied on the adherend or sprayed and then dried to form a dry film made of the foamed film composition on the adherend. The foamed film composition can be cast on the surface of a polytetrafluoroethylene film or a glass plate and dried, and then the dried film can be peeled off from the surface to make only the dried film.
As drying conditions, in order to avoid non-uniform foaming due to rapid drying, it is usually 10 to 80 ° C., preferably 20 to 60 ° C., preferably for several hours to several days. Usually, a uniform dry film is formed through the above drying.

  Although the thickness of a dry film | membrane is not specifically limited, Usually, it is about 0.1-10 mm. It is also possible to form a thicker dry film by further applying and spraying the foam film composition on the thin dry film and then drying.

By heating the obtained dry film to 180 ° C. or more, voids are generated (foamed) inside the dry film, and a uniform foam film is obtained. The reason for this foaming phenomenon is not clear, but by heating, the ammonium salt structure of the carboxylic acid formed in the alkali-soluble polymer neutralized product present in the dry film is cleaved, and the gaseous state It is presumed that ammonia is generated, thereby generating voids.
When the heating temperature is low, a foamed film cannot be obtained. The upper limit of the heating temperature is not particularly limited, but is preferably 300 ° C., more preferably 250 ° C. from the viewpoint of avoiding thermal deterioration of the foamed film itself.
The heating time is usually several tens of seconds to 30 minutes, but this foaming phenomenon proceeds relatively quickly.
After the foamed film is formed, the foamed state remains fixed by returning to room temperature.
In this heating step, the entire adherend on which the dry film is formed may be heated, or only the dry film may be heated.

  The foamed film thus produced can be applied in various fields as a heat insulating material, a soundproofing material, a lightweight member, and the like.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated concretely, this invention is not limited to the Example shown below.
In the following description, “parts” and “%” are based on weight unless otherwise specified.

The evaluation method is shown below.
1) Particle size (nm)
It is measured using a light scattering particle size measuring device (Coulter LS230: manufactured by Coulter, Inc.), and is shown as a value of volume average particle size.
2) Glass transition temperature (° C)
The aqueous polymer dispersion was cast on a framed glass plate and left in a constant temperature and humidity chamber at a temperature of 23 ° C. and a relative humidity of 50% for 48 hours to prepare a dry film.
About this film, it measured in the measurement temperature range of -100-150 degreeC by the temperature increase rate of 10 degree-C / min using the differential scanning calorimeter (EXSTAR6000DSC: Seiko Instruments Co., Ltd. product).
3) Tetrahydrofuran insoluble matter (%)
The aqueous polymer dispersion was cast on a framed glass plate and left in a constant temperature and humidity chamber at a temperature of 23 ° C. and a relative humidity of 50% for 48 hours to prepare a dry film.
After 0.3 g of this film was put in an 80 mesh wire mesh basket and immersed in 100 ml of tetrahydrofuran (THF) at 20 ° C. for 48 hours, the film remaining in the wire mesh cage was dried under reduced pressure at 100 ° C. Calculated the amount of THF insoluble matter

4) Foaming ratio The film thickness (mm) before the heat treatment of the dry film and the film thickness (mm) after the heat treatment of the dry film are measured, and the film thickness after the heat treatment with respect to the film thickness before the heat treatment is measured. Shown as a ratio.
5) Thermal conductivity (W / m · K)
Measurements were made using a rapid thermal conductivity meter (QTM-500, probe PD-11; manufactured by Kyoto Electronics Co., Ltd.) on the dried film before heat treatment and the film after heat treatment. The lower the thermal conductivity, the better the heat insulation properties.

In addition, the following thing by Kyoto Electronics Co., Ltd. was used as REFERENCE PLATE.
R3-2 (polyethylene foam) thermal conductivity 0.0362 (W / mK) at 30 ° C
R5-2 (silicon sponge) thermal conductivity 0.116 (W / mK) at 31 ° C
R2-2 (silicon rubber) Thermal conductivity 0.234 (W / mK) at 33 ° C
R1-2 (quartz glass) Thermal conductivity 1.419 (W / mK) at 29 ° C

(Production of alkali-soluble polymer neutralized product (A1))
Mixing 51 parts of methyl methacrylate, 26 parts of ethyl acrylate, 23 parts of methacrylic acid, 8 parts of octyl thioglycolate, 0.3 part of polymerizable surfactant (Aqualon HS10, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 39 parts of soft water Dispersion gave a monomer emulsion.
On the other hand, after the inside of the reactor equipped with a stirrer was purged with nitrogen, 204.2 parts of soft water was charged and heated to 85 ° C., and 19 parts of 5% potassium persulfate aqueous solution was added to the reactor, and the unit was kept at 85 ° C. The monomer emulsion was continuously added over 2 hours to react. After completing the addition of the monomer emulsion, the mixture was further maintained at 85 ° C. for 1 hour to obtain an alkali-soluble polymer. To this was added 16.1 parts of 28% aqueous ammonia, and stirring was continued for 30 minutes, followed by cooling to room temperature to obtain an aqueous alkali-soluble polymer neutralized product solution (A1) having a solid content concentration of 28%.

(Production of neutralized alkali-soluble polymer (A2))
The alkali-soluble polymer neutralized aqueous solution (A2) having a solid content concentration of 28% was the same as the above (A1) except that 22.6 parts of 20% sodium hydroxide was used as the base instead of ammonia water. )

Example 1
To an autoclave equipped with a stirrer substituted with nitrogen, 100 parts of soft water, 30 parts of an alkali-soluble polymer neutralized product (A1) in terms of solid content, 46 parts of styrene, 50 parts of 2-ethylhexyl acrylate, and 4 parts of glycidyl methacrylate were added. A monomer mixture was obtained.
In another nitrogen-substituted autoclave equipped with a stirrer, 70 parts of soft water was added, and an aqueous ammonium persulfate solution (a mixture of 11 parts of soft water and 0.5 part of ammonium persulfate) was added and maintained at 70 ° C. for 3 hours. It was dripped over. Thereafter, an aqueous ammonium persulfate solution (a mixture of 3 parts of soft water and 0.1 part of ammonium persulfate) was further added, and the reaction was continued for 4 hours while maintaining the internal temperature at 85 ° C. The conversion rate at the end of the polymerization was 99%.
After the reaction, unreacted monomers were removed, and the solid content concentration and pH were adjusted as shown in Table 1 to obtain an aqueous polymer dispersion A. Properties of the obtained aqueous polymer dispersion A are shown in Table 1.
The aqueous polymer dispersion A was cast on a framed glass plate so that the dry film thickness was about 1 mm, and the constant temperature was 23 ° C. and relative humidity (hereinafter sometimes referred to as “RH”) 50%. It dried for 72 hours or more in the constant humidity chamber, and produced the dry film | membrane. The thermal conductivity of this film was measured and the results are shown in Table 1.
Next, this dried film was heated at 220 ° C. for 5 minutes using a blowing constant temperature thermostat (DKN612; manufactured by Yamato Scientific Co., Ltd.) to obtain a foamed film. The thermal conductivity of the obtained foamed film was measured, and the results are shown in Table 1.

(Example 2)
The aqueous polymer dispersion A is cast on a framed glass plate so that the dry film thickness is about 2.5 mm, and is dried in a constant temperature and humidity chamber at 23 ° C. and RH 50% for 72 hours or more to form a dry film. Produced. The thermal conductivity of this film was measured and the results are shown in Table 1.
Next, this dried film was heated at 220 ° C. for 5 minutes using a blowing constant temperature thermostat (DKN612; manufactured by Yamato Scientific Co., Ltd.) to obtain a foamed film. The thermal conductivity of the obtained foamed film was measured, and the results are shown in Table 1.

(Example 3)
It carried out similarly to Example 1 except changing heat processing temperature from 220 degreeC to 200 degreeC. The results are shown in Table 1.
Example 4
An aqueous polymer dispersion B was obtained by reacting in the same manner as in Example 1 except that the amount of the alkali-soluble polymer neutralized product (A1) used was changed from 30 parts to 10 parts in terms of solid content.
The aqueous polymer dispersion B was cast on a framed glass plate so that the dry film thickness was about 1 mm, and dried in a constant temperature and humidity chamber at 23 ° C. and RH 50% for 72 hours or more to prepare a dry film. . The thermal conductivity of this film was measured and the results are shown in Table 1.
Next, this dried film was heated at 220 ° C. for 5 minutes using a blowing constant temperature thermostat (DKN612; manufactured by Yamato Scientific Co., Ltd.) to obtain a foamed film. The thermal conductivity of the obtained foamed film was measured, and the results are shown in Table 1.

(Example 5)
In an autoclave equipped with a stirrer substituted with nitrogen, soft water 100 parts, alkali-soluble polymer neutralized product (A1) 30 parts in terms of solid content, ethyl acrylate 70 parts, butyl acrylate 10 parts, methyl methacrylate 14 parts, glycidyl methacrylate 4 parts, 2 parts of N-methylolacrylamide was added to obtain a monomer mixture.
In another nitrogen-substituted autoclave equipped with a stirrer, 70 parts of soft water was added, and an aqueous ammonium persulfate solution (a mixture of 11 parts of soft water and 0.5 part of ammonium persulfate) was added and maintained at 70 ° C. for 3 hours. It was dripped over. Thereafter, an aqueous ammonium persulfate solution (a mixture of 3 parts of soft water and 0.1 part of ammonium persulfate) was further added, and the reaction was continued for 4 hours while maintaining the internal temperature at 85 ° C. The conversion rate at the end of the polymerization was 99%.
After the reaction, unreacted monomers were removed, and the solid content concentration and pH were adjusted as shown in Table 1 to obtain an aqueous polymer dispersion C. Properties of the obtained aqueous polymer dispersion C are shown in Table 1.
The aqueous polymer dispersion C was cast on a framed glass plate so that the dry film thickness was about 1 mm, and dried in a constant temperature and humidity chamber at 23 ° C. and RH 50% for 72 hours or more to prepare a dry film. . The thermal conductivity of this film was measured and the results are shown in Table 1.
Next, this dried film was heated at 220 ° C. for 5 minutes using a blowing constant temperature thermostat (DKN612; manufactured by Yamato Scientific Co., Ltd.) to obtain a foamed film. The thermal conductivity of the obtained foamed film was measured, and the results are shown in Table 1.

(Example 6)
In a nitrogen-substituted autoclave with a stirrer, 100 parts of soft water, 20 parts of an alkali-soluble polymer neutralized product (A1) in terms of solid content, 55 parts of styrene, 40 parts of 1,3-butadiene, 2.5 parts of glycidyl methacrylate, N -2.5 parts of methylolacrylamide and 0.2 part of t-dodecyl mercaptan were added to obtain a monomer mixture.
Into another nitrogen-substituted autoclave equipped with a stirrer, 85 parts of soft water was added, and an aqueous potassium persulfate solution (a mixture of 7 parts of soft water and 0.3 part of potassium persulfate) was added and maintained at 70 ° C. The solution was added dropwise over 3 hours. Thereafter, a potassium persulfate aqueous solution (a mixture of 7 parts of soft water and 0.3 part of potassium persulfate) was further added, and the reaction was continued for 4 hours while maintaining the internal temperature at 85 ° C. The conversion rate at the end of the polymerization was 99%.
After the reaction, unreacted monomers were removed, and the solid content concentration and pH were adjusted as shown in Table 1 to obtain an aqueous polymer dispersion D. Table 1 shows the properties of the obtained aqueous polymer dispersion D.
The aqueous polymer dispersion D was cast on a framed glass plate so that the dry film thickness was about 1 mm, and dried in a constant temperature and humidity chamber at 23 ° C. and RH 50% for 72 hours or more to prepare a dry film. . The thermal conductivity of this film was measured and the results are shown in Table 1.
Next, this dried film was heated at 220 ° C. for 5 minutes using a blowing constant temperature thermostat (DKN612; manufactured by Yamato Scientific Co., Ltd.) to obtain a foamed film. The thermal conductivity of the obtained foamed film was measured, and the results are shown in Table 1.

(Comparative Example 1)
A monomer mixture was obtained by adding 100 parts of soft water, 2 parts of sodium lauryl sulfate, 46 parts of styrene, 50 parts of 2-ethylhexyl acrylate, and 4 parts of glycidyl methacrylate to a nitrogen-substituted autoclave equipped with a stirrer.
In another nitrogen-substituted autoclave equipped with a stirrer, 70 parts of soft water was added, and an aqueous ammonium persulfate solution (a mixture of 11 parts of soft water and 0.5 part of ammonium persulfate) was added and maintained at 70 ° C. for 3 hours. It was dripped over. Thereafter, an aqueous ammonium persulfate solution (a mixture of 3 parts of soft water and 0.1 part of ammonium persulfate) was further added, and the reaction was continued for 4 hours while maintaining the internal temperature at 85 ° C. The conversion rate at the end of the polymerization was 99%.
After the reaction, unreacted monomers were removed, and the solid content concentration and pH were adjusted as shown in Table 1 to obtain an aqueous polymer dispersion E. The properties of the obtained aqueous polymer dispersion E are shown in Table 1.
The aqueous polymer dispersion E was cast on a framed glass plate so that the dry film thickness was about 1 mm, and dried in a constant temperature and humidity chamber at 23 ° C. and RH 50% for 72 hours or more to prepare a dry film. . The thermal conductivity of this film was measured and the results are shown in Table 1.
Next, this dried film was heated at 220 ° C. for 5 minutes using a blowing constant temperature thermostat (DKN612; manufactured by Yamato Scientific Co., Ltd.), but did not foam. The thermal conductivity of the film after the heat treatment was measured, and the results are shown in Table 1.

(Comparative Example 2)
An aqueous polymer dispersion F was obtained in the same manner as in Example 1 except that the alkali-soluble polymer neutralized product (A2) was used instead of the alkali-soluble polymer neutralized product (A1). Table 1 shows the properties of the obtained aqueous polymer dispersion F.
The aqueous polymer dispersion F was cast on a framed glass plate so that the dry film thickness was about 1 mm, and dried in a constant temperature and humidity chamber at 23 ° C. and RH 50% for 72 hours or more to prepare a dry film. . The thermal conductivity of this film was measured and the results are shown in Table 1.
Next, this dried film was heated at 220 ° C. for 5 minutes using a blowing constant temperature thermostat (DKN612; manufactured by Yamato Scientific Co., Ltd.), but did not foam. The thermal conductivity of the film after the heat treatment was measured, and the results are shown in Table 1.

(Comparative Example 3)
It carried out similarly to Example 1 except changing heat processing temperature from 220 degreeC to 150 degreeC. The results are shown in Table 1. However, the dried film did not foam even after heat treatment.

Table 1 shows the following.
Using an aqueous polymer dispersion E (Comparative Example 1) obtained using a surfactant usually used in emulsion polymerization, and an alkali-soluble polymer neutralized product obtained by neutralization with sodium hydroxide Even when the dried film of the aqueous polymer dispersion F (Comparative Example 2) obtained was heat-treated, no foamed film was obtained.
Moreover, although the dry film | membrane of the aqueous polymer dispersion liquid A was used, when the heat processing temperature was low, the foamed film was not obtained (comparative example 3).
For these comparative examples, a foamed film can be obtained simply by heat-treating the dried film obtained using the aqueous polymer dispersions A to D of Examples 1 to 6 at a specific temperature or higher. It can be seen that the thermal conductivity of the is lowered and the heat insulation performance is improved. In addition, the foaming state of the foamed film obtained in Examples 1-6 was homogeneous.

Claims (1)

10 to 200 parts by weight of an alkali-soluble polymer neutralized product obtained by neutralizing an alkali-soluble polymer obtained by polymerizing an ethylenically unsaturated carboxylic acid and other monomers copolymerizable therewith with ammonia. In the presence, the foamed film composition comprising an aqueous polymer dispersion obtained by emulsion polymerization of 100 parts by weight of the monomer mixture is foamed by heating the dried film obtained by drying at 180 ° C. or higher. A method for producing a foamed film .