JP6496205B2 - Thermally expandable microcapsules - Google Patents

Description

The present invention relates to a thermally expandable microcapsule having a high gas barrier property and excellent durability over a long period of time at a high temperature, a foamable thermoplastic resin masterbatch using the thermally expandable microcapsule, and a foam molded article And a stampable sheet molded body.

Thermally expandable microcapsules are used in a wide range of applications as a design-imparting agent and a lightening agent, and are also used in paints for the purpose of weight reduction such as foamed ink and wallpaper.
As such a heat-expandable microcapsule, one in which a volatile expansion agent that becomes gaseous at a temperature below the softening point of the shell polymer is included in a thermoplastic shell polymer is widely known. In Patent Document 1, an oily mixed liquid obtained by mixing a volatile expansion agent such as a low-boiling point aliphatic hydrocarbon with a monomer is added to an aqueous dispersion medium containing a dispersant together with an oil-soluble polymerization catalyst while stirring. A method for producing thermally expandable microcapsules encapsulating a volatile swelling agent by performing suspension polymerization is disclosed.

However, although the heat-expandable microcapsules obtained by this method can be thermally expanded by gasification of a volatile expansion agent at a relatively low temperature of about 80 to 130 ° C., they expand when heated at a high temperature or for a long time. There has been a problem that the expansion ratio is reduced by the escape of gas from the microcapsules. In addition, due to problems with heat resistance and strength of the thermally expandable microcapsules, a phenomenon called “sag” has occurred and sometimes collapsed at high temperatures.

On the other hand, Patent Document 2 has a thermal expansion in which a vinyl monomer having an epoxy group or an isocyanate group and a vinyl monomer having a hydroxyl group or an amino group are included as structural units and the 5% thermal weight loss temperature is 280 to 350 ° C. Microcapsules are disclosed.
Such thermally expandable microcapsules are said to have excellent mechanical strength even under high temperature and high humidity.
However, since the gas barrier property is still low, there is a problem that it cannot withstand high-temperature and long-time heating, and there is a problem that gas escapes during heating and foaming does not occur in the foaming process.

Patent Document 3 discloses that the foaming start temperature Ts and the maximum foaming temperature Tmax satisfy the relationship of 120 <Ts ≦ 250, 0 ≦ Tmax−Ts <30, so that the followability to the molded body is increased and the weight is reduced. A method for obtaining a compact is disclosed.
However, since the particles obtained by the method of Patent Document 3 have low gas barrier properties, there is a problem that foaming displacement is small and does not swell so much. Moreover, there also existed a problem that it could not endure high temperature and long time heating.

Japanese Examined Patent Publication No. 42-26524 JP 2005-272633 A Japanese Patent No. 5512404

The present invention relates to a thermally expandable microcapsule having a high gas barrier property and excellent durability over a long period of time at a high temperature, a foamable thermoplastic resin masterbatch using the thermally expandable microcapsule, and a foam molded article And it aims at providing a stampable sheet molding.

The present invention relates to a thermally expandable microcapsule in which a volatile expansion agent is encapsulated as a core agent in a shell made of a polymer, and the shell includes a nitrile monomer, a monomer having an amide group, and a molecule. A monomer composition containing a compound having a glycidyl group is polymerized, the foaming start temperature Ts is 190 ° C. or higher, and the foaming start temperature Ts ′ after heating at 180 ° C. for 80 seconds is 150 to 170 ° C., The weight reduction rate after heating at 180 ° C. for 5 minutes is 3.0% by weight or less, and the weight reduction rate after heating from 30 ° C. to the maximum foaming temperature Tmax at 5 ° C./minute is 12.0% by weight. A thermally expandable microcapsule characterized by the following.
The present invention is described in detail below.

The present inventors use a predetermined monomer as a monomer constituting the shell, and set the foaming start temperature Ts, the foaming start temperature Ts ′ after heating under a predetermined condition, and the weight reduction rate within a predetermined range. Thus, it has been found that the foaming start temperature is high, good thermal expansibility is obtained over a long period of time, and because it has excellent gas barrier properties, it is difficult to sag and has excellent durability. The invention has been completed.

In particular, car ceiling materials are manufactured through a foam molding process at a high temperature for a long period of time. Therefore, heat-expandable microcapsules used as foaming agents have higher durability and heat resistance for a longer time than before. Is required. However, the heat-expandable microcapsules of the present invention have high gas barrier properties and excellent durability at high temperatures, and therefore can be suitably used for automotive ceiling materials.

In the thermally expandable microcapsule of the present invention, a preferable lower limit of the foaming start temperature Ts is 190 ° C. When the foaming start temperature is lower than 190 ° C., the foam may be slightly foamed during the production of the raw material of the molded body, and may not expand in the foaming process of the molded body.
A preferable lower limit of the foaming start temperature is 190 ° C, more preferably 195 ° C, still more preferably 200 ° C, and a preferable upper limit is 215 ° C, more preferably 210 ° C.
The foaming start temperature Ts can be measured, for example, using a TMA apparatus (for example, TMAQ400EM type manufactured by TA Instruments Co., Ltd.) at a temperature rising rate of 5 ° C./min.

The heat-expandable microcapsule of the present invention has a foaming start temperature Ts ′ of 150 to 170 ° C. after heating at 180 ° C. for 80 seconds. If Ts ′ is less than 150 ° C., the heat-expandable microcapsules will sag immediately after foaming in the foaming step of the molded body, which causes a problem that the molded body does not expand to the target magnification. When exceeding, the problem is that the thermally expandable microcapsules do not swell in the foaming step of the molded body, so that the molded body does not swell to the target magnification. The preferable lower limit of Ts ′ is 150 ° C., more preferably 155 ° C., still more preferably 160 ° C., and the preferable upper limit is 170 ° C., more preferably 165 ° C.

The maximum foaming temperature (Tmax) of the thermally expandable microcapsule of the present invention is not particularly limited, but a preferable lower limit is 190 ° C. When the maximum foaming temperature is less than 190 ° C., the heat-expandable microcapsules have low heat resistance, are liable to burst and shrink at high temperatures, and cannot be foamed at a high foaming ratio. In addition, when the maximum foaming temperature is less than 190 ° C., for example, when master batch pellets are produced using thermally expandable microcapsules, foaming occurs due to shearing force during pellet production, and an unfoamed master Batch pellets may not be manufactured stably. Also, when producing a stampable sheet molded body made of thermally expandable microcapsules, inorganic fibers and resin, foaming occurs due to heat during press molding, and the stampable sheet molded body cannot be manufactured stably. is there. As for the maximum foaming temperature of the said thermally expansible microcapsule, a more preferable minimum is 200 degreeC and a preferable upper limit is 220 degreeC.
In the present specification, the maximum foaming temperature means the temperature at which the thermally expandable microcapsule reaches the maximum displacement when the diameter is measured while heating the thermally expandable microcapsule from room temperature. .

The thermally expandable microcapsule of the present invention has a weight loss rate of 3.0% by weight or less after heating at 180 ° C. for 5 minutes. If the weight reduction rate exceeds 3.0% by weight, the thermally expandable microcapsule may not be sufficiently foamed in the foaming step of the molded body. A preferred upper limit is 2.0% by weight. The preferable lower limit of the weight reduction rate is not particularly limited, but is 0.1% by weight.
The weight reduction rate can be calculated from [(weight before heating−weight after heating) / weight before heating] × 100.
The weight reduction rate after heating at 180 ° C. for 5 minutes can be measured using, for example, TG-DTA.

The heat-expandable microcapsules of the present invention have a weight loss rate of 12.0% by weight or less after being heated from 25 ° C. to the maximum foaming temperature Tmax at 5 ° C./min. If the weight reduction rate after heating from 25 ° C. to the maximum foaming temperature Tmax at 5 ° C./min exceeds 12.0% by weight, the thermally expandable microcapsules may not sufficiently foam in the foaming process of the molded body. is there. The upper limit is preferably 11.5% by weight, more preferably 11.0% by weight, and still more preferably 10.0% by weight. The preferable lower limit of the weight reduction rate is not particularly limited, but is 0.1% by weight.
In addition, the weight reduction rate after heating at 25 degreeC / min from the said 25 degreeC to the maximum foaming temperature Tmax can be measured using TG-DTA etc., for example.

The thermally expandable microcapsule of the present invention has a structure in which a volatile expansion agent is included as a core agent in a shell made of a polymer. By having such a structure, for example, by molding the thermally expandable microcapsule of the present invention in a matrix resin, the core agent becomes gaseous by heating during molding, and the shell softens. The foamed article can be produced.

In the present invention, the shell is obtained by polymerizing a monomer composition containing a nitrile monomer, a monomer having an amide group, and a compound having a glycidyl group in the molecule. By using such a monomer composition, Ts, Ts ′, and the weight reduction rate can be within a predetermined range.

When the monomer composition contains the nitrile monomer, the resulting heat-expandable microcapsules have high heat resistance and gas barrier properties.
The nitrile monomer is not particularly limited, and examples thereof include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumaronitrile, or a mixture thereof. Of these, acrylonitrile and methacrylonitrile are particularly preferred. These may be used independently and 2 or more types may be used together.

The preferable lower limit of the content of the nitrile monomer in the monomer composition is 80% by weight. When the content of the nitrile monomer is less than 80% by weight, the gas barrier property is lowered, and the expansion ratio may be lowered.
A more preferred lower limit is 85% by weight, and a preferred upper limit is 98% by weight.

The monomer composition for forming the polymer contains a monomer having an amide group. When the monomer composition contains the monomer having the amide group, the resulting heat-expandable microcapsule binds the amide group and the compound having a glycidyl group in the molecule, which will be described later, by heat at the time of heat foaming. Therefore, the heat resistance and durability can be further improved.

Examples of the monomer having an amide group include (meth) acrylamide, N-substituted (meth) acrylamide, N, N-substituted (meth) acrylamide, N-vinylamide and the like.
Examples of the (meth) acrylamide include acrylamide and methacrylamide.
Examples of the N-substituted (meth) acrylamide include N-methylolacrylamide, N-methylolmethacrylamide, N-methoxymethylacrylamide, N-isopropoxymethylacrylamide, N-butoxymethylacrylamide, N-isobutoxymethylacrylamide, N-octyloxymethylacrylamide, N-carboxymethyleneoxymethylacrylamide, isopropylacrylamide and the like can be mentioned.
Examples of the N, N-substituted (meth) acrylamide include dimethylacrylamide, diethylacrylamide, dimethylaminopropylacrylamide and the like.
Examples of the N-vinylamide include N-vinylacetamide.
When N-substituted (meth) acrylamide or N, N-substituted (meth) acrylamide is used as the monomer having the amide group, the number of carbon atoms of the substituent on nitrogen is preferably 1 to 4, more preferably nitrogen. The number of carbon atoms of the above substituent is 1-2.
Among the monomers having an amide group, acrylamide and methacrylamide are particularly preferable from the viewpoint of high heat resistance and gas barrier properties.

The content of the monomer having an amide group in the monomer composition is preferably 1% by weight and preferably 18% by weight with respect to 100% by weight of the total monomer composition.
When the content of the monomer having an amide group is 1% by weight or more, the effect obtained by bonding with a compound having a glycidyl group in a molecule, which will be described later, during heating and foaming is further improved. When the content of the monomer having an amide group is 18% by weight or less, induction of particle aggregation during polymerization can be suppressed. A more preferred lower limit is 2% by weight, a more preferred upper limit is 15% by weight, and a particularly preferred lower limit is 3% by weight.

The content ratio of the monomer having an amide group to the compound having a glycidyl group in the molecule (a monomer having an amide group / a compound having a glycidyl group in the molecule) has a preferable lower limit of 1.5 and a preferable upper limit of 12.
When the content of the monomer having an amide group with respect to the compound having a glycidyl group is within the above range, the effect obtained by bonding with a compound having a glycidyl group in the molecule, which will be described later, during heating and foaming is further increased. It becomes good.

The monomer composition for forming the polymer contains a compound having a glycidyl group in the molecule. While the glycidyl group and the amide group undergo a curing reaction at 140 to 300 ° C., the temperature during polymerization is generally 100 ° C. or lower, and therefore the glycidyl group and amide group are The curing reaction does not occur.
On the other hand, since the temperature at the time of heat expansion of the thermally expandable microcapsule is generally 100 to 300 ° C., the above glycidyl group reacts with the amide group at a high temperature at the time of heat foaming, thereby providing high heat resistance and gas barrier properties. Can be realized. Further, the shape can be maintained even after expansion, and the retainability is excellent.
The compound having a glycidyl group in the molecule cures not at the time of polymerization of the monomer composition but at the time of heat expansion of the thermally expandable microcapsule, so that the expansion at the time of expansion is not hindered and the expansion ratio is increased. Can do.
The compound having a glycidyl group in the molecule may constitute a shell polymer as a monomer, and may not be a polymer but contained in the shell. .

The compound having a glycidyl group in the molecule is preferably a compound having at least one polymerizable unsaturated bond in the molecule. By having at least one polymerizable unsaturated bond in the molecule, the polymerizable group is incorporated into the main chain of the shell polymer, so that the curability at the time of heat expansion of the thermally expandable microcapsule is stronger. Therefore, the heat resistance and durability can be greatly improved.
Moreover, as a compound which has a glycidyl group in the said molecule | numerator, what has two or more glycidyl groups in a molecule | numerator is more preferable. By having two or more glycidyl groups in the molecule, the curability can be made stronger. In particular, the amide group and the glycidyl group are more strongly bonded by heat at the time of heating and foaming, and the heat resistance and durability can be greatly improved.

Examples of the compound having a glycidyl group in the molecule include a glycidyl group-containing monomer and an epoxy resin.
In addition, a glycidyl group containing monomer means the monomer which has a glycidyl group and a radically polymerizable double bond.
Moreover, an epoxy resin is a compound which has two or more oxirane rings (epoxy group) in a molecule | numerator, and does not have a radically polymerizable double bond.

Examples of the glycidyl group-containing monomer include epoxy (meth) acrylate. As epoxy (meth) acrylate, glycidyl methacrylate, glycidyl acrylate, allyl glycidyl ether, 4-hydroxybutyl acrylate glycidyl ether, phenol type epoxy diacrylate, allyl alcohol type epoxy diacrylate, 1,6-hexanediol type epoxy diacrylate Bisphenol type epoxy diacrylate, phthalic acid type epoxy diacrylate, polypropylene glycol type epoxy diacrylate (n = 1, 3, 11), polyethylene glycol type epoxy dimethacrylate (n = 1, 2, 9) and the like.

Examples of the epoxy resin include bisphenol A type epoxy resin (JER-828: manufactured by Mitsubishi Chemical Corporation), hydrogenated bisphenol A type epoxy resin (YX-8000: manufactured by Mitsubishi Chemical Corporation), and bisphenol F type epoxy resin (JER- 807: manufactured by Mitsubishi Chemical Corporation), phenol novolac type epoxy resin (JER-152: manufactured by Mitsubishi Chemical Corporation), cresol novolac type epoxy resin (N-660: manufactured by DIC Corporation), biphenyl type epoxy resin (YX-4000: Mitsubishi Chemical Corporation) And dicyclopentadiene type epoxy resin (HP-7200L: manufactured by DIC), glycidylamine type epoxy resin (JER-630: manufactured by Mitsubishi Chemical Corporation), and the like.

Also, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, triethylene glycol diglycidyl ether, polyethylene glycol di Glycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane polyglycidyl ethers may be used.
In addition, the repeating number of the oxyethylene part of polyethyleneglycol diglycidyl ether is not specifically limited, For example, the repeating number of the oxyethylene part is 2, 4, 9, 13, or 23 (n = 2, 4, 9, 13, or 23). Polyethylene glycol diglycidyl ether that is) can be used. In addition, the number of repetitions of the oxypropylene portion of the polypropylene glycol diglycidyl ether is not particularly limited. For example, the number of repetitions of the oxypropylene portion is 2, 3 or 11 (n = 2, 3 or 11). Can be used.
A compound having two or more glycidyl ether structures in the molecule may be used.
Examples of the compound having two or more glycidyl ether structures in the molecule include, for example, polyglycidyl ether of a compound in which 0 to 1 mol of epichlorohydrin is added to 1 mol of glycerin and a mixture thereof, or epichlorohydrin to 1 mol of ethylene glycol. Also included are polyglycidyl ethers of compounds to which 0 to 2 moles have been added, and mixtures thereof.
Among the compounds having a glycidyl group in the molecule, glycidyl methacrylate is preferable from the viewpoint of improving heat resistance and durability by reacting with the amide group at a high temperature.

The content of the compound having a glycidyl group in the molecule in the monomer composition is preferably 0.1% by weight and preferably 15% by weight with respect to 100% by weight of the total monomer composition. When the content of the compound having a glycidyl group in the molecule is 0.1% by weight or more, the effect obtained by bonding with an amide group at the time of heat foaming is further improved. When the content of the compound having a glycidyl group in the molecule is 15% by weight or less, induction of particle aggregation during polymerization can be suppressed. A more preferred lower limit is 0.5% by weight, a more preferred upper limit is 10% by weight, a still more preferred lower limit is 1% by weight, and a still more preferred upper limit is 5% by weight.

The monomer composition may further contain a crosslinkable monomer having two or more double bonds in the molecule. The crosslinkable monomer has a role as a crosslinking agent. By containing the crosslinkable monomer, the strength of the shell can be enhanced, and the cell wall is less likely to break during thermal expansion. The crosslinkable monomer having two or more double bonds in the molecule does not contain a compound having a glycidyl group in the molecule.

Examples of the crosslinkable monomer include monomers having two or more radical polymerizable double bonds. Specific examples include divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and triethylene glycol. Di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, Polyethylene glycol di (meth) acrylate having a weight average molecular weight of 200 to 600, glycerin di (meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene oxide Modified trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, triallyl formal tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dimethylol-tricyclodecandi (Meth) acrylate etc. are mentioned. Among these, trifunctional ones such as trimethylolpropane tri (meth) acrylate and bifunctional (meth) acrylates such as polyethylene glycol are relatively uniformly crosslinked in the shell mainly composed of acrylonitrile. Since the microcapsules that are thermally expanded even in a high-temperature region exceeding 210 ° C. are difficult to contract and easily maintain the expanded state, a so-called “sag” phenomenon can be suppressed and is preferably used.

The minimum with preferable content of the said crosslinkable monomer in the said monomer composition is 0.1 weight%, and a preferable upper limit is 1.0 weight%.
When the content of the crosslinkable monomer is less than 0.1% by weight, the effect as a crosslinking agent may not be exhibited. When the crosslinkable monomer is added in an amount exceeding 1.0% by weight, thermal expansion occurs. The expansion ratio of the conductive microcapsule is reduced. The minimum with more preferable content of the said crosslinkable monomer is 0.15 weight%, and a more preferable upper limit is 0.5 weight%.

In addition to the nitrile monomer, the monomer having an amide group, the compound having a glycidyl group in the molecule, and a crosslinkable monomer, the monomer composition may include other monomers that can be copolymerized with the nitrile monomer (hereinafter, (It may be simply referred to as another monomer).
The other monomers are not particularly limited and can be appropriately selected depending on the properties required for the thermally expandable microcapsules to be obtained. For example, methyl acrylate, ethyl acrylate, butyl acrylate, dicyclohexane Examples include acrylic acid esters such as pentenyl acrylate, methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, and isobornyl methacrylate, vinyl monomers such as vinyl chloride, vinylidene chloride, vinyl acetate, and styrene. .
These may be used independently and 2 or more types may be used together.

When the monomer composition contains the other monomer, the content of the other monomer in the monomer composition is not particularly limited, but a preferable upper limit with respect to 100% by weight of the total monomer composition is 40% by weight.
When the content of the other monomer exceeds 40% by weight, the content of the nitrile monomer is decreased, and the resulting heat-expandable microcapsule has reduced heat resistance and gas barrier properties. Shrinkage tends to occur and foaming may not be possible at a high expansion ratio.

In the monomer composition, the content of the monomer having a carboxyl group is preferably 0.001 part by weight or less with respect to 100 parts by weight of the total monomer components, and it is particularly preferable that the monomer composition does not contain a monomer having a carboxyl group.
By containing the monomer having the carboxyl group, the residual monomer of the monomer having the carboxyl group mainly promotes oxidative degradation of the base resin used for molding, so the molded product is colored yellowish brown. In some cases, the residual monomer volatilizes due to heating during molding, and an irritating odor peculiar to acid spreads, which may adversely affect the working environment.

Examples of the monomer having a carboxyl group include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, and cinnamic acid, and unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid, and citraconic acid. An acid etc. are mentioned. These salts and anhydrides are also included.

It is preferable to add a polymerization initiator to the monomer composition.
The polymerization initiator is not particularly limited, and examples thereof include dialkyl peroxide, diacyl peroxide, peroxyester, peroxydicarbonate, and azo compound.
The dialkyl peroxide is not particularly limited, and examples thereof include methyl ethyl peroxide, di-t-butyl peroxide, dicumyl peroxide, isobutyl peroxide and the like.

The diacyl peroxide is not particularly limited, and examples thereof include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, and the like.

The peroxy ester is not particularly limited, and examples thereof include t-butyl peroxypivalate, t-hexyl peroxypivalate, t-butyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, 1- Cyclohexyl-1-methylethylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, cumylperoxyneodecanoate, (α, α-bis-neodecanoylper And oxy) diisopropylbenzene.

The peroxydicarbonate is not particularly limited. For example, bis (4-t-butylcyclohexyl) peroxydicarbonate, di-n-propyl-peroxydicarbonate, diisopropyl peroxydicarbonate, di (2-ethylethyl) Peroxy) dicarbonate, dimethoxybutyl peroxydicarbonate, di (3-methyl-3-methoxybutylperoxy) dicarbonate, and the like.

The azo compound is not particularly limited. For example, 2,2′-azobisisobutyronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis ( 2,4-dimethylvaleronitrile), 1,1′-azobis (1-cyclohexanecarbonitrile) and the like.

If necessary, the monomer composition may further contain a stabilizer, an ultraviolet absorber, an antioxidant, an antistatic agent, a flame retardant, a silane coupling agent, a colorant, and the like.

The weight average molecular weight of the polymer obtained by polymerizing the monomer composition as described above is not particularly limited, but the preferable lower limit is 100,000 and the preferable upper limit is 2 million.
When the weight average molecular weight is less than 100,000, the resulting heat-expandable microcapsule has low shell strength, tends to rupture and shrink at high temperatures, and may not foam at a high expansion ratio. When the said weight average molecular weight exceeds 2 million, the intensity | strength of a shell becomes too high and the foaming performance may fall in the thermally expansible microcapsule obtained.

The shell preferably has a gel fraction of 70% or less when heated at 75 ° C. for 24 hours. Thereby, in the foaming process of a molded object, a thermally expansible microcapsule may not fully foam. Moreover, it is preferable that it is 30% or more.
The shell preferably has a gel fraction of not less than 60% when heated at 190 ° C. for 5 minutes. Thereby, the sag by heating may be suppressed. Moreover, it is preferable that it is 95% or less.
The gel fraction can be measured by swelling thermally expanded microcapsules in N, N-dimethylformamide, separating and drying the precipitate.

The thermally expandable microcapsule of the present invention includes a volatile expansion agent as a core agent.
In this specification, the volatile swelling agent refers to a substance that becomes gaseous at a temperature below the softening point of the shell.

Examples of the volatile swelling agent include low molecular weight carbonization such as ethane, ethylene, propane, propene, n-butane, isobutane, butene, isobutene, n-pentane, isopentane, neopentane, n-hexane, heptane, and petroleum ether. Examples include hydrogen, chlorofluorocarbons such as CCl ₃ F, CCl ₂ F ₂ , CClF ₃ , and CClF ₂ -CClF ₂ , tetraalkylsilanes such as tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, and trimethyl-n-propylsilane. It is done. Of these, isobutane, n-butane, n-pentane, isopentane, n-hexane, petroleum ether, and mixtures thereof are preferred. These volatile swelling agents may be used alone or in combination of two or more.

In the heat-expandable microcapsule of the present invention, it is preferable to use a low-boiling hydrocarbon having 10 or less carbon atoms among the above-described volatile expansion agents. By using such a hydrocarbon, it is possible to obtain a thermally expandable microcapsule having a high expansion ratio and promptly starting foaming.
Moreover, it is good also as using the thermal decomposition type compound which thermally decomposes by heating and becomes a gaseous state as a volatile expansion | swelling agent.

In the thermally expandable microcapsule of the present invention, the preferred lower limit of the content of the volatile swelling agent used as the core agent is 10% by weight, and the preferred upper limit is 25% by weight.
The thickness of the shell varies depending on the content of the core agent, but if the core agent content is reduced and the shell becomes too thick, the foaming performance is reduced, and if the core agent content is increased, the shell strength is reduced. To do. When the content of the core agent is 10 to 25% by weight, it becomes possible to achieve both prevention of sag of the thermally expandable microcapsule and improvement of foaming performance.

The volume average particle diameter of the thermally expandable microcapsule of the present invention is not particularly limited, but a preferable lower limit is 10 μm and a preferable upper limit is 100 μm. When the volume average particle diameter is less than 10 μm, for example, when foaming a thermally expandable microcapsule into a matrix resin and molding, the resulting foamed molded article has too small bubbles, resulting in insufficient weight reduction. There is. When the volume average particle diameter exceeds 100 μm, for example, when the thermally expandable microcapsules are blended with a matrix resin and molded, the foamed foam obtained is too large, which is problematic in terms of strength and the like. Sometimes. The volume average particle diameter is more preferably a lower limit of 15 μm and a more preferable upper limit of 60 μm.

The method for producing the heat-expandable microcapsule of the present invention is not particularly limited. For example, a step of preparing an aqueous dispersion medium, a nitrile monomer, a monomer having an amide group, and a molecule in the aqueous dispersion medium The monomer composition is polymerized by performing a step of dispersing an oily mixture containing a compound having a glycidyl group and a volatile swelling agent and a step of polymerizing the monomer composition. Examples include a method of obtaining a thermally expandable microcapsule containing a volatile expansion agent as a core agent in a shell containing the polymer formed.

In the step of preparing the aqueous dispersion medium, for example, an aqueous dispersion medium containing the dispersion stabilizer is prepared by adding water, a dispersion stabilizer, and, if necessary, an auxiliary stabilizer to the polymerization reaction vessel. Moreover, you may add alkali metal nitrite, stannous chloride, stannic chloride, potassium dichromate, etc. to the said aqueous dispersion medium as needed.

The dispersion stabilizer is not particularly limited. For example, silica, calcium phosphate, magnesium hydroxide, aluminum hydroxide, ferric hydroxide, barium sulfate, calcium sulfate, sodium sulfate, calcium oxalate, calcium carbonate, calcium carbonate, carbonate Examples include barium and magnesium carbonate.

The auxiliary stabilizer is not particularly limited, and examples thereof include a condensation product of diethanolamine and an aliphatic dicarboxylic acid, a condensation product of urea and formaldehyde, a water-soluble nitrogen-containing compound, polyethylene oxide, tetramethylammonium hydroxide, gelatin, Examples include methyl cellulose, polyvinyl alcohol, dioctyl sulfosuccinate, sorbitan ester, and various emulsifiers.
The water-soluble nitrogen-containing compound is not particularly limited, and examples thereof include polyvinyl pyrrolidone, polyethyleneimine, polyoxyethylene alkylamine, polydialkylaminoalkyl (meth) acrylate represented by polydimethylaminoethyl methacrylate and polydimethylaminoethyl acrylate, Examples thereof include polydialkylaminoalkyl (meth) acrylamides represented by polydimethylaminopropylacrylamide and polydimethylaminopropylmethacrylamide, polyacrylamide, polycationic acrylamide, polyamine sulfone, and polyallylamine. Of these, polyvinylpyrrolidone is preferred.

The combination of the dispersion stabilizer and the auxiliary stabilizer is not particularly limited. For example, a combination of colloidal silica and a condensation product, a combination of colloidal silica and a water-soluble nitrogen-containing compound, magnesium hydroxide or calcium phosphate and an emulsifier. And the like. Among these, a combination of colloidal silica and a condensation product is preferable, and the condensation product is preferably a condensation product of diethanolamine and an aliphatic dicarboxylic acid, a condensation product of diethanolamine and adipic acid, diethanolamine and A condensation product with itaconic acid is particularly preferred.

When colloidal silica is used as the dispersion stabilizer, the amount of colloidal silica added is not particularly limited and can be appropriately determined depending on the particle size of the target thermally expandable microcapsule, but is preferably based on 100 parts by weight of the total monomer components. The lower limit is 1 part by weight, the preferred upper limit is 20 parts by weight, the more preferred lower limit is 2 parts by weight, and the more preferred upper limit is 10 parts by weight.
In addition, when the condensation product or the water-soluble nitrogen-containing compound is used as the auxiliary stabilizer, the addition amount of the condensation product or the water-soluble nitrogen-containing compound is not particularly limited, and the target thermally expandable microcapsule Although it can be determined appropriately depending on the particle size, the preferred lower limit with respect to 100 parts by weight of all monomer components is 0.05 parts by weight, and the preferred upper limit is 2 parts by weight.

In addition to the dispersion stabilizer and the auxiliary stabilizer, an inorganic salt such as sodium chloride or sodium sulfate may be further added to the aqueous dispersion medium. By adding such an inorganic salt, a thermally expandable microcapsule having a more uniform particle shape can be obtained.
The amount of the inorganic salt added is not particularly limited, but the preferable upper limit with respect to 100 parts by weight of all monomer components is 100 parts by weight.

The aqueous dispersion medium is prepared by blending the dispersion stabilizer and the auxiliary stabilizer with deionized water, and the pH of the deionized water is appropriately determined according to the type of the dispersion stabilizer and auxiliary stabilizer used. Can do. For example, when silica such as colloidal silica is used as the dispersion stabilizer, an acid such as hydrochloric acid is added as necessary to adjust the pH of the system to 3 to 4, and polymerization can be performed under acidic conditions in the steps described later. Done. When magnesium hydroxide or calcium phosphate is used as the dispersion stabilizer, the system is adjusted to be alkaline, and polymerization is performed under alkaline conditions in the steps described later.

In producing the thermally expandable microcapsule of the present invention, a step of dispersing an oily mixed solution containing the monomer composition and the volatile swelling agent in the aqueous dispersion medium is then performed.
In this step, the monomer composition and the volatile swelling agent may be separately added to the aqueous dispersion medium to prepare the oily mixture in the aqueous dispersion medium. Are mixed into an oily mixture and then added to the aqueous dispersion medium. At this time, after preparing the oily mixed liquid and the aqueous dispersion medium in separate containers in advance and mixing them with stirring in another container, the oily mixed liquid is dispersed in the aqueous dispersion medium, You may add to a polymerization reaction container.
A polymerization initiator is used to polymerize the monomer in the monomer composition. The polymerization initiator may be added to the oily mixture in advance, and the aqueous dispersion medium, the oily mixture, May be added after stirring and mixing in the polymerization reaction vessel.

In the step of dispersing the oily mixture containing the monomer composition and the volatile swelling agent in the aqueous dispersion medium, the oily mixture is emulsified and dispersed in the aqueous dispersion medium with a predetermined particle size.
The method of emulsifying and dispersing is not particularly limited. For example, a method of stirring with a homomixer (for example, manufactured by Tokushu Kika Kogyo Co., Ltd.) or the like, a method of passing through a static dispersing device such as a line mixer or an element type static dispersing device. Etc. The aqueous dispersion medium and the oily mixed liquid may be separately supplied to the static dispersion apparatus, or a dispersion liquid that has been mixed and stirred in advance may be supplied.

In producing the thermally expandable microcapsule of the present invention, a step of polymerizing the monomer composition is then performed. The method for polymerizing is not particularly limited, and examples thereof include a method for polymerizing the monomer composition by heating.
Thus, a volatile swelling agent as a core agent is formed on a shell made of a polymer obtained by polymerizing a monomer composition containing a nitrile monomer, a monomer having an amide group, and a compound having a glycidyl group in the molecule. Is obtained. The obtained thermally expandable microcapsules may be subsequently subjected to a dehydration step, a drying step, and the like.

The use of the heat-expandable microcapsule of the present invention is not particularly limited. For example, the slurry in which the heat-expandable microcapsule, surfactant, inorganic fiber, and resin of the present invention are suspended in water is filtered and press-molded. Thus, a stampable sheet molded body can be manufactured. In addition, by heating and stamping the stampable sheet molded body, it is possible to obtain a foamed stampable sheet molded body having heat insulating properties, heat insulating properties, sound insulating properties, sound absorbing properties, vibration proofing properties, weight reduction, and the like. it can. Such a stampable sheet molded body is also one aspect of the present invention. Note that the stampable sheet molded body is a sheet of a composite material in which a resin and inorganic fibers are mixed, and can be formed into a foamed stampable sheet molded body by heating.

The stampable sheet molded article of the present invention is formed, for example, by producing a nonwoven fabric using the thermally expandable microcapsules of the present invention, inorganic fibers, and a thermoplastic resin, and compression molding using a press machine.
The stampable sheet molded body of the present invention may be formed by either a wet process or a dry process, but is preferably formed by a wet process.

Examples of the method for forming the stampable sheet molded article of the present invention using a wet process include the following methods. Specifically, first, a heat-expandable microcapsule of the present invention, a thermoplastic resin, and inorganic fibers are mixed to prepare a mixed emulsion. The obtained mixed emulsion is subjected to dehydration filtration to produce a nonwoven fabric. Next, the obtained non-woven fabric is dried at a temperature lower than the expansion start temperature of the thermally expandable microcapsule of the present invention to remove the aqueous medium. Furthermore, the thermoplastic resin is melted and pressed while being heated at a temperature lower than the thermal expansion start temperature of the thermally expandable microcapsule of the present invention, and then cooled. In this way, the stampable sheet molded body of the present invention can be formed.

Examples of the inorganic fibers include amorphous fibers such as glass fibers, carbon fibers, and rock wool, polycrystalline fibers such as alumina fibers, and single crystal fibers such as wollastonite and potassium titanate fibers.

Although the fiber diameter of the said inorganic fiber is not specifically limited unless the objective of this invention is inhibited, It is preferable that it is 0.1-100 micrometers, and it is more preferable that it is 1-30 micrometers.
When the average diameter of the inorganic fibers is within the preferable range, the inorganic fibers are sufficiently entangled, and the stampable sheet molded body can be sufficiently reinforced.

Although the cut length of the said inorganic fiber is not specifically limited unless the objective of this invention is inhibited, It is preferable that it is 1-100 mm, and it is more preferable that it is 10-100 mm.
When the cut length of the inorganic fiber is within the preferable range, the inorganic fibers are sufficiently entangled, and the stampable sheet molded body can be sufficiently reinforced.

The content of the inorganic fiber in the mixed emulsion is not particularly limited, but is preferably 0.1 to 20% by weight, more preferably 0.3 to 10% by weight, and still more preferably 0.5 to 5% by weight. . When the content of the inorganic fiber is within the preferable range, the dispersibility of the inorganic fiber in the obtained stampable sheet molded body is improved, and the strength of the stampable sheet molded body can be made sufficient. .

The resin is not particularly limited as long as the object of the present invention is not impaired. For example, a thermoplastic resin can be used.
Examples of the thermoplastic resin include general thermoplastic resins such as polyvinyl chloride, polystyrene, polypropylene, polypropylene oxide, and polyethylene; engineering plastics such as polybutylene terephthalate, nylon, polycarbonate, and polyethylene terephthalate. Further, thermoplastic elastomers such as ethylene, vinyl chloride, olefin, urethane, and ester may be used, or these resins may be used in combination.

The thermoplastic resin is preferably a resin powder.
The average particle size of the resin powder is not particularly limited, but is preferably 10 to 1000 μm, more preferably 20 to 400 μm.
When the average particle diameter of the resin powder is within the preferable range, the inorganic fibers can be sufficiently bound to each other, and the strength of the stampable sheet molded body can be made sufficient.
The average particle diameter of the resin powder can be measured, for example, by a method such as microscopic observation or a light transmission particle diameter measuring method.

The content of the thermoplastic resin in the mixed emulsion is not particularly limited, but is preferably 0.1 to 20% by weight, more preferably 0.3 to 10% by weight, still more preferably 0.5 to 5% by weight. is there.
When the content of the thermoplastic resin is within the preferable range, the inorganic fibers can be sufficiently bound to each other, and the strength of the stampable sheet molded body can be made sufficient.

The content of the thermally expandable microcapsule of the present invention in the mixed emulsion is not particularly limited, but is preferably 0.01 to 10% by weight, more preferably 0.05 to 5% by weight, and still more preferably 0.1 to 0.1%. 2% by weight. When the content of the thermally expandable microcapsule of the present invention is within the above preferred range, the stampable sheet molded body is sufficiently heated when heated at a temperature higher than the expansion start temperature of the thermally expandable microcapsule of the present invention. A high expansion ratio can be obtained.

The mixed emulsion may contain a flame retardant.
The flame retardant is not particularly limited, nitrogen-containing compounds such as urea and melamine cyanurate, phosphoric acid compounds such as polyphosphoric acid, organic halogen compounds such as chlorinated paraffin and decabromobiphenyl ether, aluminum hydroxide and magnesium hydroxide, etc. And hydrated metal oxides. These may be used independently and 2 or more types may be used together.

The mixed emulsion may contain a surfactant. The surfactant is not particularly limited, and examples thereof include a cationic surfactant, an anionic surfactant, and a nonionic surfactant.

In addition, by blending the thermally expandable microcapsules of the present invention into a matrix resin and molding using a molding method such as injection molding, extrusion molding, etc., heat insulation, heat insulation, sound insulation, sound absorption, vibration isolation, It is possible to produce a foamed molded article having a weight reduction or the like. The heat-expandable microcapsule of the present invention is suitably applied to foam molding having a step of heating at a high temperature because it can hardly foam and shrink even at a high temperature and can be foamed at a high expansion ratio.

Master batch pellets in which a matrix resin such as a thermoplastic resin is added to the thermally expandable microcapsules of the present invention are molded using a molding method such as injection molding, and the above thermally expandable microcapsules are formed by heating during molding. A foamed molded product can be produced by foaming. Such a foamable thermoplastic resin masterbatch is also one aspect of the present invention.

The thermoplastic resin is not particularly limited as long as the object of the present invention is not impaired. For example, general thermoplastic resins such as polyvinyl chloride, polystyrene, polypropylene, polypropylene oxide, and polyethylene; polybutylene terephthalate, nylon, Engineering plastics such as polycarbonate and polyethylene terephthalate are listed. Further, thermoplastic elastomers such as ethylene, vinyl chloride, olefin, urethane, and ester may be used, or these resins may be used in combination.

The amount of thermally expandable microcapsules added to 100 parts by weight of the thermoplastic resin is preferably 0.5 to 20 parts by weight, more preferably 1 to 10 parts by weight. Moreover, it can also use together with chemical foaming agents, such as sodium hydrogencarbonate (bicarbonate) and ADCA (azo type).

The method for producing the master batch pellet is not particularly limited. For example, a matrix resin such as a thermoplastic resin and raw materials such as various additives are kneaded in advance using a same-direction twin-screw extruder or the like. Next, after heating to a predetermined temperature and adding a foaming agent such as the thermal expansion microcapsule of the present invention, the kneaded product obtained by further kneading is cut into a desired size with a pelletizer to form a pellet. And a method of preparing master batch pellets.
Alternatively, a master batch pellet in the form of a pellet may be manufactured by kneading a matrix resin such as a thermoplastic resin or a raw material such as a thermally expandable microcapsule with a batch kneader and then granulating with a granulator. .
The kneader is not particularly limited as long as it can knead without destroying the thermally expandable microcapsules, and examples thereof include a pressure kneader and a Banbury mixer.

According to the present invention, a heat-expandable microcapsule that has high expansion ratio and durability at high temperature and is less likely to cause coloring and odor when used in foam molding, and foamability using the heat-expandable microcapsule A thermoplastic resin master batch, a foamed molded product, a stampable sheet molded product, and a method for producing the thermally expandable microcapsule can be provided.

Examples of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

(Examples 1-11, Comparative Examples 1-9)
In a polymerization reaction vessel, 250 parts by weight of water, 25 parts by weight of colloidal silica (20% by weight, manufactured by Asahi Denka Co., Ltd.) and 0.8 parts by weight of polyvinylpyrrolidone (manufactured by BASF) as a dispersion stabilizer, 1.8% by weight of 1N hydrochloric acid The aqueous dispersion medium was prepared.
Subsequently, the monomer composition, the volatile swelling agent, and the polymerization initiator (0.8 parts by weight of 2,2′-azobisisobutyronitrile, 2,2′-azobis (2 , 4-dimethylvaleronitrile) 0.6 parts by weight) was added to an aqueous dispersion medium and suspended to prepare a dispersion. The resulting dispersion was stirred and mixed with a homogenizer, charged into a nitrogen-substituted pressure polymerization reactor, and reacted at 60 ° C. for 20 hours while applying pressure (0.5 MPa) to obtain a reaction product. The obtained reaction product was repeatedly filtered and washed with water, and then dried to obtain thermally expandable microcapsules.
In addition, as a compound having a glycidyl group in the molecule, glycidyl methacrylate (manufactured by Kyoeisha Chemical Co., Ltd., number of glycidyl groups: 1, number of polymerizable unsaturated bonds: 1), bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, JER828) , The number of glycidyl groups: 2, the number of polymerizable unsaturated bonds: 0) and trimethylolpropane polyglycidyl ether (EX-321 manufactured by Nagase ChemteX Corporation, the number of glycidyl groups: 3, the number of polymerizable unsaturated bonds: 0) was used.
In addition to isopentane and isooctane, isoparaffinic petroleum solvent (ExxonMobil, Isopar H) was used as the volatile swelling agent.

(Evaluation)
The following evaluation was performed about the thermally expansible microcapsule obtained by the Example and the comparative example. The results are shown in Table 1.

(1) Foam start temperature Ts, maximum foam temperature Tmax
Using a thermomechanical analyzer (TMA) (TMA2940, manufactured by TA instruments), the foaming start temperature Ts and the maximum foaming temperature Tmax were measured. Specifically, 25 μg of a sample is placed in an aluminum container having a diameter of 7 mm and a depth of 1 mm, and heated from 80 ° C. to 250 ° C. at a temperature rising rate of 5 ° C./min with a force of 0.1 N applied from above. Then, the displacement in the vertical direction of the measurement terminal was measured, and the temperature at which the displacement began to rise was defined as the foaming start temperature. Further, the expansion ratio was measured, and the temperature at which the expansion ratio was the maximum was defined as the maximum expansion temperature.

(2) Foam start temperature Ts ′
1 g of a sample was put in an aluminum cup and heated at 180 ° C. for 80 seconds with a blow dryer.
About the sample after a heating, foaming start temperature Ts' was measured using said TMA.

(3) Weight reduction rate (weight reduction rate after heating at 180 ° C. for 5 minutes)
A sample 1.5 mg was heated to 180 ° C. at a rate of temperature increase from 30 ° C. to 80 ° C./min using a differential thermothermal gravimetric simultaneous measurement apparatus (TG / DTA6300, manufactured by Seiko Instruments Inc.). The weight loss rate after 5 minutes was evaluated.

(Weight reduction rate after heating from 30 ° C to Tmax)
About 1.5 mg of a sample, the weight reduction rate when heated from 30 ° C. to Tmax of each sample at a rate of temperature increase of 5 ° C./min was evaluated using a differential thermothermal gravimetric simultaneous measurement apparatus.

(4) Gel fraction (normal gel fraction)
0.1 g (a [g]) of the thermally expandable microcapsule obtained and 20.0 g of N, N-dimethylformamide were weighed in a glass test tube and heated at 75 ° C. for 24 hours. After heating, the mixture was centrifuged at 20000 rpm for 30 minutes with a centrifuge, and the supernatant was discarded. The precipitated undissolved material was vacuum-dried for 48 hours in a 75 ° C. vacuum dryer, and the weight (b [g]) of the dried undissolved material was measured. Subsequently, the gel fraction (A) at the time of non-heating was computed from the following formula.
Gel fraction at non-heating (A) = (b / a) × 100 (%)

(Gel fraction after heating at 190 ° C for 5 minutes)
The thermally expandable microcapsule was weighed in a 0.1 g aluminum cup and heated in a hot air oven at 190 ° C. for 5 minutes. 0.1 g (a [g]) of the heated sample and 20.0 g of N, N-dimethylformamide were weighed in a glass test tube and heated at 75 ° C. for 24 hours. After heating, the mixture was centrifuged at 20000 rpm for 30 minutes with a centrifuge, and the supernatant was discarded. The precipitated undissolved material was vacuum-dried for 48 hours in a 75 ° C. vacuum dryer, and the weight (b [g]) of the dried undissolved material was measured. Next, the gel fraction (B) after heating at 190 ° C. for 5 minutes was calculated from the following formula.
Gel fraction after heating at 190 ° C. for 5 minutes (B) = (b / a) × 100 (%)

(5) Using a heat-resistant heating foaming microscope (manufactured by Japan High-Tech), spray a small amount of thermally expandable microcapsules on the stage and observe the expansion behavior up to 280 ° C while heating at 5 ° C / min. The expansion ratio D220 at 220 ° C. when the diameter of the thermally expandable microcapsule was expanded by 1 was measured. The case where D220 is less than 2 times is “×”, the case where it is 2 times or more and less than 3 times is “◯”, the case where it is 3 times or more and less than 4 times is “○”, and 4 times. The case where it was above was evaluated as "XXX".

(6) Using a durable heating foaming microscope (manufactured by Japan High-Tech), the expansion behavior was observed under the same conditions as heat resistance, and the temperature width (ΔT) at which the foaming ratio was 2 times or more was measured. The case where ΔT is less than 40 ° C. is “x”, the case where it is 40 ° C. or more and less than 50 ° C. is “◯”, the case where it is 50 ° C. or more and less than 60 ° C. is “○○”, 60 ° C. The case where it was above was evaluated as "XXX".

(7) When using a compression-resistant thermomechanical measuring device (TMA: manufactured by TA Instruments), the foam is heated and foamed at a temperature rising rate of 30 ° C./min up to a load of 0.01 mN and a heating temperature of 180 ° C. The foam displacement was 100%. Thereafter, the reduction rate of the foam displacement when the load was applied up to 0.05 mN was measured. The case where the reduction rate of the foam displacement is less than 20% is “XX”, the case where it is 20% or more and less than 50% is “XX”, and the case where it is 50% or more and less than 80% is “ The case where it was 80% or more was evaluated as “×”.

(8) Molding ratio of molded body (production of stampable sheet molded body)
To 1 L of ion-exchanged water, add 4 g of the obtained thermally expandable microcapsules, 8 g of glass fiber (fiber diameter 13 μm, cut length 20 mm) and 10 g of polypropylene resin powder (melting point 165 ° C., average particle size 300 μm), and disperse and mix. An emulsion was obtained. The obtained mixed emulsion was filtered under reduced pressure using a stainless steel mesh (Φ100 μm) to obtain a nonwoven fabric. The obtained nonwoven fabric was dried in a heating oven at 110 ° C. for 20 minutes, and then pressed at 2 MPa for 10 minutes in a press machine heated to 170 ° C. Thereafter, a cooling press was performed to obtain a stampable sheet molded body.

(Molding ratio of molded body)
The obtained stampable sheet molded body was cut into 50 mm squares. The thickness of each corner was measured, and the average was taken as the thickness (X) of the stampable sheet molded body before foaming. After heating the stampable sheet compact for 4 minutes in an oven at a temperature of 200 ° C., the thickness of each corner was measured, and the average was taken as the thickness (Y) after foaming of the stampable sheet compact. Next, the molding magnification (loft%) of the compact was calculated from the following formula.
Molding ratio of molded body = (Y / X) × 100 (loft%)
When the molding magnification is less than 300 loft%, “X”, when it is 300 loft% or more and less than 500 loft%, “◯”, when it is 500 loft% or more and less than 700 loft%, “◯◯”, 700 loft % Was evaluated as “XX”.

According to the present invention, a thermally expandable microcapsule having a high expansion ratio and durability at a high temperature, a foamable thermoplastic resin masterbatch using the thermally expandable microcapsule, a foamed molded product, a stampable sheet molded product, and A method for producing the thermally expandable microcapsule can be provided.

Claims (7)

A thermally expandable microcapsule in which a volatile expansion agent is encapsulated as a core agent in a polymer shell,
The shell is formed by polymerizing a monomer composition containing a nitrile monomer, a monomer having an amide group, and a compound having a glycidyl group in the molecule,
The foaming start temperature Ts is 190 ° C. or higher,
The foaming start temperature Ts ′ after heating at 180 ° C. for 80 seconds is 150 to 170 ° C.,
The weight loss after heating at 180 ° C. for 5 minutes is 3.0% by weight or less, and
A thermally expandable microcapsule characterized by having a weight reduction rate of not more than 12.0% by weight after heating from 30 ° C. to a maximum foaming temperature Tmax at 5 ° C./min. The monomer composition contains 80% by weight or more of a nitrile monomer, 1 to 18% by weight of a monomer having an amide group, and 0.1 to 15% by weight of a compound having a glycidyl group in the molecule. Item 2. A thermally expandable microcapsule according to Item 1. The thermally expandable microcapsule according to claim 1 or 2, wherein the monomer composition contains 1.0% by weight or less of a crosslinkable monomer having two or more double bonds in the molecule. The shell has a gel fraction of 70% or less when heated at 75 ° C for 24 hours, and a gel fraction of 60% or more when heated at 190 ° C for 5 minutes. Thermally expandable microcapsules. 5. A foamable thermoplastic resin masterbatch comprising the thermally expandable microcapsules according to claim 1, 2, 3 or 4, and a thermoplastic resin. A foamed molded article comprising the thermally expandable microcapsule according to claim 1, 2, 3, or 4, or the foamable thermoplastic resin masterbatch according to claim 5. A stampable sheet molded article comprising the thermally expandable microcapsule according to claim 1, 2, 3, or 4, an inorganic fiber, and a resin.