WO2017195438A1

WO2017195438A1 - Method for producing foamed molding

Info

Publication number: WO2017195438A1
Application number: PCT/JP2017/007855
Authority: WO
Inventors: 晋太郎野村; 鈴木　康弘; 奈緒子栗生; 石川　勝之; 俊蔵遠藤; 哲男江尻
Original assignee: 株式会社クレハ
Priority date: 2016-05-11
Filing date: 2017-02-28
Publication date: 2017-11-16

Abstract

Provided is a foamed molding producing method capable of producing a foamed molding using microspheres (hereinafter, MS) while reducing energy consumption and improving productivity. The method for producing a foamed molding according to the present invention comprises step A for obtaining an unfoamed molding comprising a thermally-foamable composition, and a step for heating and foaming the unfoamed molding at T2 (°C), wherein: the thermally-foamable composition contains MS and a substrate comprising a thermoplastic resin, a thermosetting resin, and/or fibers; the MS has an outer shell containing a polymer, and a foaming agent enclosed in the outer shell; step A includes a step for heating the thermally-foamable composition at T1 (°C); the foaming start temperature and maximum foaming temperature of the MS after the heating are lower than these temperatures before the heating by 10°C or more and 5°C or more, respectively; T1 is 105°C or more but less than the foaming start temperature Ts of the MS before the heating; and T2 is Ts-40°C or more but less than the maximum foaming temperature -3°C of the MS before the heating.

Description

Method for producing foam molded article

The present invention relates to a method for producing a foam molded article.

“Microspheres”, also called heat-expandable microcapsules, are obtained by microcapsulating a volatile foaming agent with an outer shell made of a polymer, and usually have heat-foaming properties (“heat-foaming microcapsules”). Fair "). In the production of microspheres, generally, when suspension polymerization of a polymerizable monomer and a polymerizable mixture containing a foaming agent is allowed to proceed in an aqueous dispersion medium, the outer shell ( Shell) is formed.

For the polymer forming the outer shell, a thermoplastic resin having a good gas barrier property is generally used. The polymer forming the outer shell is softened by heating. As the blowing agent, generally, a low-boiling compound such as a hydrocarbon that becomes gaseous at a temperature below the softening point of the polymer forming the outer shell is used.

When microspheres are heated, the foaming agent vaporizes and expands, acting on the outer shell. At the same time, the elastic modulus of the polymer that forms the outer shell decreases sharply, so that it suddenly decreases at a certain temperature. Expansion occurs. This temperature is called the “foaming start temperature”. When heated above the foaming start temperature, foam particles (closed cells) are formed due to the expansion phenomenon, and when further heated, the foaming agent permeates the thinned outer shell and the internal pressure decreases, Foam particles shrink (sag phenomenon). The temperature at which the volume increase due to the expansion phenomenon is maximized is called “maximum foaming temperature”.

Microspheres are used in a wide range of fields such as designability-imparting agents, functionality-imparting agents, and lightening agents by utilizing the above-described properties of forming foam particles. For example, it is used by being added to polymer materials such as synthetic resins (thermoplastic resins and thermosetting resins) and rubber, paints, inks and the like. When higher performance is required in each application field, the required level for microspheres also increases, and for example, improvement in processing characteristics such as heat resistance is required.

As microspheres having heat resistance and usable at high temperatures, for example, the monomer as the main component is acrylonitrile (I), a monomer (II) containing a carboxyl group, Proposing a microsphere that uses a copolymer obtained by polymerizing a monomer (III) having a group that reacts with a carboxyl group as an outer shell and encloses a liquid having a boiling point lower than the softening temperature of the copolymer. (Patent Document 1).

International Publication No. 99/43758

By the way, if the foaming start temperature is high, it is difficult to foam the microsphere unless a large amount of heat is input. In addition, foaming can be performed most efficiently by foaming near the maximum foaming temperature, but if the maximum foaming temperature is high, it is still required to input a large amount of heat. As described above, when the foaming start temperature and the maximum foaming temperature are high, a large amount of heat is required to produce a foamed molded article by heating and foaming the microsphere, and it is difficult to achieve energy saving and productivity improvement. .

The present invention has been made in view of the above-described problems, and provides a method for producing a foamed molded product that can produce a foamed molded product using microspheres while saving energy and improving productivity. For the purpose.

The present inventors can solve the above problems by using microspheres in which the foaming start temperature and the maximum foaming temperature are lowered within a predetermined range by heat treatment at a predetermined temperature lower than the foaming start temperature. As a result, the present invention has been completed.

An aspect of the present invention is a method for producing a foam molded article,
The method includes a step (A) of obtaining an unfoamed molded article comprising a thermally foamable composition, and a step (B) of heating and foaming the unfoamed molded body at a temperature T2 (° C.).
The thermally foamable composition contains microspheres and at least one substrate selected from the group consisting of thermoplastic resins, thermosetting resins, and fibers,
The microsphere includes an outer shell containing a polymer, and a foaming agent enclosed in the outer shell,
Step (A) includes a step (a) of heat-treating the thermally foamable composition at a temperature T1 (° C.),
The foaming start temperature of the microsphere after the heat treatment in the step (a) is 10 ° C. or more lower than the foaming start temperature of the microsphere before the heat treatment in the step (a),
The maximum foaming temperature of the microsphere after the heat treatment in the step (a) is 5 ° C. or more lower than the maximum foaming temperature of the microsphere before the heat treatment in the step (a),
The temperatures T1 and T2 are methods that satisfy the following formulas (1) and (2), respectively.
105 ≦ T1 <Ts (° C.) (1)
Ts-40 ≦ T2 <Tmax-3 (° C.) (2)
(In the formula, Ts (° C.) represents the foaming start temperature of the microsphere before heat treatment in step (a), and Tmax (° C.) represents the maximum foaming of the microsphere before heat treatment in step (a). Represents temperature.)

In step (A), it is preferable to obtain the unfoamed molded body by molding the thermally foamable composition heat-treated in step (a). Alternatively, in step (A), after molding the thermal foamable composition before heat treatment in step (a), the molded thermal foamable composition is heat treated in step (a), thereby It is preferable to obtain a foamed molded product.

The polymer preferably contains a copolymer containing a structural unit derived from (meth) acrylonitrile and a structural unit derived from (meth) acrylic acid ester.

According to the present invention, it is possible to provide a method for producing a foamed molded product that can produce a foamed molded product using microspheres while saving energy and improving productivity.

FIG. 1 is a graph showing the foaming behavior of microspheres in Examples or Comparative Examples. FIG. 2 is another graph showing the foaming behavior of the microspheres in the examples.

<Method for producing foam molded article>
The method for producing a foamed molded product according to the present invention includes a step (A) of obtaining an unfoamed molded product comprising a thermally foamable composition, and a step of heating and foaming the unfoamed molded product at a temperature T2 (° C.) (B ) And. The thermally foamable composition contains microspheres and at least one substrate selected from the group consisting of thermoplastic resins, thermosetting resins, and fibers.

[Base material]
The substrate is at least one selected from the group consisting of a thermoplastic resin, a thermosetting resin, and fibers. Each of a thermoplastic resin, a thermosetting resin, and a fiber can be used individually or in combination of 2 or more types. The thermoplastic resin is not particularly limited. For example, polyvinyl chloride (PVC), polypropylene (PP), ethylene vinyl acetate copolymer (EVA), thermoplastic elastomer (TPE), ethylene / methyl methacrylate copolymer (Hereinafter also referred to as “EMMA”). Examples of the thermosetting resin include ethylene-propylene-diene rubber (EPDM), silicone rubber, and epoxy resin. The fiber is not particularly limited, and examples thereof include glass fiber, carbon fiber, metal fiber, pulp fiber, and synthetic fiber.

[Microsphere]
The microspheres used in the present invention include an outer shell containing a polymer and a foaming agent enclosed in the outer shell, and usually have thermal foaming properties (“thermal foaming microspheres”). Microspheres having such a structure can generally be produced by suspension polymerization of at least one polymerizable monomer in the presence of a foaming agent in an aqueous dispersion medium containing a dispersion stabilizer. it can. In the thermally foamable composition, the content of microspheres is preferably 1 to 120 parts by weight, more preferably 1 to 70 parts by weight, and still more preferably 1 to 60 parts by weight with respect to 100 parts by weight of the substrate. Parts, even more preferably 1 to 50 parts by weight. When the content of the microsphere is within the above range, it is easy to obtain a foamed molded article having a good foamed state.

(1) Vinyl monomer Examples of the polymer forming the outer shell include a polymer containing a structural unit derived from a vinyl monomer, and foaming starts by heat treatment at a temperature lower than the foaming start temperature. A copolymer containing a structural unit derived from (meth) acrylonitrile and a structural unit derived from (meth) acrylic acid ester (hereinafter referred to as “(meth) acrylonitrile” because it is easy to obtain a microsphere having a reduced temperature and maximum foaming temperature. -It is also preferable to contain (meth) acrylic acid ester copolymer ". In the present specification, “(meth) acrylonitrile” means acrylonitrile and / or methacrylonitrile, in other words, at least one nitrile monomer selected from the group consisting of acrylonitrile and methacrylonitrile. means. In the present specification, “(meth) acrylic acid ester” means acrylic acid ester and / or methacrylic acid ester, in other words, at least one selected from the group consisting of acrylic acid ester and methacrylic acid ester. Of unsaturated acid ester monomers.

Examples of the acrylate ester include, but are not limited to, methyl acrylate, ethyl acrylate, butyl acrylate, and dicyclopentenyl acrylate. Examples of the methacrylic acid ester include, but are not limited to, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and isobornyl methacrylate.

The (meth) acrylonitrile / (meth) acrylic acid ester copolymer contains structural units derived from other vinyl monomers from the viewpoints of foamability, gas barrier properties, heat resistance, and / or solvent resistance. Also good. Examples of other vinyl monomers include nitrile monomers other than (meth) acrylonitrile, such as α-chloroacrylonitrile, α-ethoxyacrylonitrile, and fumaronitrile; vinyl chloride; vinylidene chloride; vinyl acetate; chloroprene, isoprene, butadiene Conjugated dienes such as: N-phenylmaleimide, N-naphthylmaleimide, N-cyclohexylmaleimide, methylmaleimide and other N-substituted maleimides; acrylic acid, methacrylic acid, crotonic acid, maleic anhydride and other unsaturated acids; styrene, α -Vinyl aromatic compounds such as methylstyrene and halogenated styrene.

In the (meth) acrylonitrile / (meth) acrylic acid ester copolymer, the total of the structural units derived from (meth) acrylonitrile and the structural units derived from (meth) acrylic acid ester, the structural units derived from (meth) acrylonitrile The content is preferably 50 to 99% by weight, more preferably 55 to 99% by weight, even more preferably 60 to 99% by weight, and the content of the structural unit derived from (meth) acrylic acid ester is preferably It is 1 to 50% by weight, more preferably 1 to 45% by weight, and still more preferably 1 to 40% by weight. When the content is within the above range, the structural unit derived from (meth) acrylonitrile is a main component, and thus the foaming start temperature of the formed microsphere can be increased.

From the viewpoint of improving foamability, gas barrier properties, heat resistance, and / or solvent resistance in the (meth) acrylonitrile / (meth) acrylic acid ester copolymer without impairing the object of the present invention, The total content of the structural unit derived from (meth) acrylonitrile and the structural unit derived from (meth) acrylic ester with respect to the whole structural unit derived from the body is preferably 90 to 100% by weight, more preferably 92 to 99%. The content of structural units derived from other vinyl monomers is preferably from 0 to 10% by weight, more preferably from 1 to 8% by weight, and still more preferably from 95% to 98% by weight. Is 2 to 5% by weight.

From the viewpoint of moisture resistance and the like, the polymer forming the outer shell preferably does not contain a structural unit derived from an unsaturated acid such as acrylic acid, methacrylic acid, crotonic acid or maleic anhydride.

(2) Crosslinkable monomer In the present invention, a vinyl monomer and a crosslinkable monomer as described above can be used in combination as the polymerizable monomer. By using a crosslinkable monomer in combination, processability, foaming characteristics, heat resistance, solvent resistance and the like can be improved. As the crosslinkable monomer, a polyfunctional compound having two or more polymerizable carbon-carbon double bonds (—C═C—) is used. Examples of the polymerizable carbon-carbon double bond include a vinyl group, a methacryl group, an acrylic group, and an allyl group. Two or more polymerizable carbon-carbon double bonds may be the same or different from each other.

Examples of the crosslinkable monomer include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof; diethylenically unsaturated carboxylic acids such as ethylene glycol diacrylate, diethylene glycol diacrylate, ethylene glycol dimethacrylate, and diethylene glycol dimethacrylate. Bifunctional crosslinkability such as acid esters; acrylates or methacrylates derived from aliphatic terminal alcohols such as 1,4-butanediol and 1,9-nonanediol; divinyl compounds such as N, N-divinylaniline and divinyl ether; Monomer.

Examples of other crosslinkable monomers include trifunctional or higher polyfunctional crosslinkable monomers such as trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, and triacryl formal. A monomer is mentioned.

Among the crosslinkable monomers, a bifunctional crosslinkable monomer having two polymerizable carbon-carbon double bonds is preferable in terms of easily balancing the foamability and processability. The bifunctional crosslinkable monomer may be directly or indirectly via a flexible chain derived from a diol compound selected from the group consisting of polyethylene glycol, polypropylene glycol, alkyl diol, alkyl ether diol, and alkyl ester diol. In particular, the compound is preferably a compound having a structure in which two polymerizable carbon-carbon double bonds are linked.

Examples of the bifunctional crosslinkable monomer having a structure in which two polymerizable carbon-carbon double bonds are linked via the above-described flexible chain include polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, and polypropylene glycol diester. Acrylate, polypropylene glycol dimethacrylate, alkyl diol diacrylate, alkyl diol dimethacrylate, alkyl ether diol diacrylate, alkyl ether diol dimethacrylate, alkyl ester diol diacrylate, alkyl ester diol dimethacrylate, and mixtures of two or more thereof Can be mentioned.

When a bifunctional crosslinkable monomer having such a flexible chain is used as the crosslinkable monomer, the temperature dependence of the elastic modulus of the outer shell polymer is reduced while maintaining a high expansion ratio. In addition, even when subjected to a shearing force in a kneading process, a calendar process, an extrusion process, an injection molding process, or the like, a microsphere can be obtained which is less likely to break the outer shell or dissipate the encapsulated gas.

The use ratio of the crosslinkable monomer is preferably 5 parts by weight or less (that is, 0 to 5 parts by weight), more preferably 0.01 to 5 parts by weight, and still more based on 100 parts by weight of the vinyl monomer. The amount is preferably 0.05 to 4 parts by weight, particularly preferably 0.1 to 3 parts by weight. It is preferable that the use ratio of the crosslinkable monomer is within the above range from the viewpoint that the processability is hardly lowered and the thermoplasticity of the polymer forming the outer shell is hardly lowered and the foaming is hardly difficult.

(3) Foaming agent The foaming agent is a substance that becomes a gas when heated. As the blowing agent, hydrocarbons having a boiling point corresponding to the foaming start temperature can be used. For example, methane, ethane, ethylene, propane, propene, n-butane, isobutane, butene, isobutene, n-pentane, isopentane. , Hydrocarbons such as neopentane, n-hexane, isohexane, n-heptane, isoheptane, n-octane, isooctane, n-nonane, isononane, n-decane, isodecane, n-dodecane, isododecane, petroleum ether, isoparaffin mixture, and the like isomeric mixtures _{_{_{_{thereof; CCl 3 F, CCl 2 F}}}} 2, CClF 3, chlorofluorocarbons such as CClF ₂ -CClF 2; tetramethylsilane, trimethylethyl silane, trimethyl isopropyl silane, tetra alkyl such as trimethyl -n- propyl silane Run, and the like. A foaming agent can be used individually or in combination of 2 or more types. Among these, isobutane, n-butane, n-pentane, isopentane, n-hexane, isooctane, isododecane, and isomer mixtures thereof, petroleum ether, and a mixture of two or more of these are preferable. Further, if desired, a compound that is thermally decomposed by heating to become a gas may be used.

The ratio of the foaming agent encapsulated in the microsphere is preferably 5 to 50% by weight, more preferably 7 to 40% by weight, based on the total amount. Therefore, it is desirable to adjust the use ratio of the polymerizable monomer and the foaming agent such that the outer shell polymer and the foaming agent have the above ratio after the polymerization.

(4) Microsphere production method The microsphere used in the present invention is a method of suspension polymerization of at least one polymerizable monomer in the presence of a foaming agent in an aqueous dispersion medium containing a dispersion stabilizer. Can be manufactured. A more specific production method is not particularly limited, and a known method can be used.

(5) Microsphere The microsphere used in the present invention has a structure in which a foaming agent is enclosed in an outer shell formed from a polymer. The polymer forming the outer shell is formed by polymerization of a polymerizable monomer (mainly vinyl monomer). By using a vinyl monomer and a crosslinkable monomer together, the outer shell polymer is formed. The temperature dependence of the elastic modulus can be reduced.

As the polymer, for example, a polymer containing a structural unit derived from a vinyl monomer, preferably a (meth) acrylonitrile / (meth) acrylate copolymer, is used for heat treatment at a temperature lower than the foaming start temperature. By doing so, it is easy to obtain microspheres in which the foaming start temperature and the maximum foaming temperature are lowered.

The average particle size of the microspheres used in the present invention is not particularly limited, and is preferably 1 to 200 μm, more preferably 3 to 150 μm, and particularly preferably 5 to 100 μm. When the average particle size of the microspheres is within the above range, the foamability tends to be sufficient; in the field where a beautiful appearance is required, the smoothness of the surface is not easily impaired; and the shearing force during processing This is preferable in that the resistance is unlikely to be insufficient.

The content of the foaming agent in the microspheres used in the present invention is preferably 5 to 50% by weight, more preferably 7 to 40% by weight, based on the total weight. When the content of the foaming agent is within the above range, the expansion ratio is difficult to be insufficient, and the thickness of the outer shell does not become too thin. It is easy to be suppressed from causing rupture.

The foaming start temperature of the microsphere used in the present invention is 10 ° C. or more, preferably 20 to 60 ° C., more preferably 30 to 50 ° C. by heat-treating the thermally foamable composition at a temperature T1 (° C.). Even more preferably, the temperature falls by 35 to 45 ° C.

The maximum foaming temperature of the microspheres used in the present invention is 5 ° C. or more, preferably 10 to 40 ° C., more preferably 12 to 30 ° C. by heat-treating the thermally foamable composition at a temperature T1 (° C.). Even more preferably, the temperature falls by 15 to 25 ° C.

[Step (A)]
In the step (A), an unfoamed molded body made of a thermally foamable composition is obtained. As described above, the thermally foamable composition contains microspheres and at least one substrate selected from the group consisting of thermoplastic resins, thermosetting resins, and fibers. Step (A) includes a step (a) of heat-treating the thermally foamable composition at a temperature T1 (° C.). The timing for heat-treating the thermally foamable composition at a temperature T1 (° C.) is not particularly limited, and may be before molding the thermally foamable composition or after molding the thermally foamable composition. Specifically, it is as follows. That is, in one embodiment, in the step (A), the unfoamed molded body is obtained by molding the thermally foamable composition heat-treated in the step (a). In another embodiment, in the step (A), after the heat-foamable composition before the heat treatment in the step (a) is molded, the molded heat-foamable composition is heat-treated in the step (a). Thus, the unfoamed molded body is obtained. In any case, in the step (A), the thermally foamable composition is heat treated at a temperature T1 (° C.), and at the same time, the unheated microspheres are heat treated at a temperature T1 (° C.). Thereby, the foaming start temperature and maximum foaming temperature of a microsphere can be reduced.

The temperature T1 (° C.) satisfies the following formula (1).
105 ≦ T1 <Ts (° C.) (1)
(In the formula, Ts (° C.) represents the foaming start temperature of the microsphere before heat treatment in the step (a).)

In the step (a) in the step (A), the thermally foamable composition is heat treated at a temperature T1 (° C.), and as a result, the unheated microsphere is heat treated at a temperature T1 (° C.). There are no particular limitations, and examples include extrusion, hot pressing, and drying. Specific examples of extrusion include a method in which the microspheres that have not been heat-treated are blended with the base material, particularly a thermoplastic resin, and pellets are produced by extrusion under conditions in which the microspheres do not substantially foam. It is done. At that time, by setting the temperature of the die used for extrusion to T1, the thermally foamable composition is heat-treated at a temperature T1 (° C.), and the untreated microspheres are heated at a temperature T1 (° C.). It can be heat treated. As a specific example of the hot press, there is a method in which the microspheres that have not been heat-treated are mixed with a thermoplastic resin, and the microspheres are pressed using a hot press machine under conditions where the microspheres are not substantially foamed. By setting the press temperature to T1, the thermally foamable composition can be heat treated at a temperature T1 (° C.), and the untreated microspheres can be heat treated at a temperature T1 (° C.). As a specific example of drying, disperse the unheated microspheres together with the base material in water, and make this dispersion, that is, pour the dispersion on a papermaking screen to obtain a non-woven deposit. The method of drying this under the conditions where the said microsphere does not substantially foam is mentioned. By setting the temperature at the time of drying to T1, the thermally foamable composition can be heat-treated at temperature T1 (° C.), and the untreated microspheres can be heat-treated at temperature T1 (° C.). . Further, the mixture of the thermoplastic resin and the unheated microspheres is heated to a temperature T1 (° C.) using an oven or the like under a condition in which the microspheres are not substantially foamed. The thermally foamable composition may be heat-treated at (° C.), and the unheated microspheres may be heat-treated at a temperature T1 (° C.).

[Step (B)]
In the step (B), the unfoamed molded body is heated and foamed at a temperature T2 (° C.). Thereby, the target foaming molding can be obtained. Specifically, for example, the foamed molded article is obtained by foaming the microspheres in the pellets and the nonwoven fabric-like deposit in the description of the specific method of the step (A) at a temperature T2 (° C.). Can do.

The temperature T2 (° C.) satisfies the following formula (2).
Ts-40 ≦ T2 <Tmax-3 (° C.) (2)
(In the formula, Ts is as described above, and Tmax (° C.) represents the maximum foaming temperature of the untreated microsphere.)

As is apparent from the formula (2), the microspheres are foamed in a state where energy costs are suppressed by heating and foaming at a temperature of 40 ° C. lower than Ts and lower than 3 ° C. lower than Tmax. Obtainable.
The temperature T2 (° C.) specifically satisfies the following formula (2-1), and more specifically satisfies the following formula (2-2).
150 ≦ T2 <Tmax-3 (° C.) (2-1)
150 ≦ T2 <205 (2-2)

When the formula (2-1) is satisfied, the foamed microspheres can be foamed by heating and foaming at a temperature of 150 ° C. or more and less than 3 ° C. lower than Tmax, while suppressing the energy cost. it can.

When the formula (2-2) is satisfied, the microspheres can be foamed by heating and foaming at 150 ° C. or more and less than 205 ° C. while suppressing the energy cost to obtain a foam molded article.

[Foaming start temperature]
The foaming start temperature can be measured by a thermomechanical analyzer (hereinafter referred to as “TMA”). Specifically, in the present invention, the foaming start temperature refers to a microsphere alone or a 1: 1 (weight ratio) mixture of microspheres and EMMA as a sample, and a temperature rising rate of 5 ° C. using TMA. The temperature at the time when the displacement of the height starts when the height displacement of the portion occupied by the sample is continuously measured.

[Maximum foaming temperature]
The maximum foaming temperature can be measured by TMA. Specifically, in the present invention, the foaming start temperature refers to a microsphere alone or a 1: 1 (weight ratio) mixture of microspheres and EMMA as a sample, and a temperature rising rate of 5 ° C. using TMA. The temperature at the time when the height displacement was the largest when the height displacement of the portion occupied by the sample was continuously measured.

[Foamed molded product]
The foamed molded product obtained by the production method according to the present invention is reduced in weight by foam molding using the microspheres, and is given design as necessary. The shape of the foamed molded product is not particularly limited, and may be any of a sheet shape, a rod shape, a pipe shape, a block shape, and other arbitrary shapes. The foamed molded product can be suitably used as a resin molded product for automobiles because it is reduced in weight by foam molding and is excellent in soundproofing effect and heat insulating effect.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited to these examples.

[Measurement of foaming behavior]
The foaming start temperature and the maximum foaming temperature of the microspheres in Examples or Comparative Examples were measured. Specifically, 1 mg of a sample is put in a container, and the temperature is increased at a heating rate of 5 ° C./min using a thermomechanical analyzer (model number “TMA / SDTA840”, manufactured by METTLER TRADE Co., Ltd.). The displacement of the occupied portion was measured continuously. The temperature at the time when the height displacement started was defined as the unheated foaming start temperature (Ts), and the temperature at the time when the height displacement was the largest was defined as the maximum foaming temperature (Tmax). At that time, the homogeneity of the foaming behavior was determined according to the following evaluation criteria. The results of Comparative Examples 0 to 3 and Examples 1 to 3 are shown in Table 1, and the results of Comparative Example 0 and Examples 4 to 9 are shown in Table 2. The height displacement graph is shown in FIG. 1 for Comparative Examples 1 to 3 and Examples 1 to 3, and in FIG. 2 for Examples 4 to 9.
○: When the peak (including the shoulder peak) is present alone in the height displacement graph, it is determined that the homogeneity of the foaming behavior is good.
X: In the graph of the displacement of the height, when there are a plurality of peaks (including shoulder peaks), it is determined that the homogeneity of the foaming behavior is poor.

[Measurement of foamability]
The displacement value at 188 ° C. was read during the measurement of the foaming behavior. Moreover, the microsphere in an Example or a comparative example was made to foam, and the foaming density was measured. Specifically, 0.5 g of a sample was weighed into an aluminum cup and heated and foamed in an oven at 180 ° C. for 5 minutes, and then the resulting foam was taken out and placed in a 50 ml volumetric flask and diluted with isopropanol. The weight of the sample was measured, and the density of the foam (foaming density) was determined from the weight after measuring up. From these results, foamability was determined according to the following evaluation criteria. The results of Comparative Examples 0 to 3 and Examples 1 to 3 are shown in Table 1, and the results of Comparative Example 0 and Examples 4 to 9 are shown in Table 2.
○ Displacement value at 188 ° C .: 500 μm or more and foaming density: 0.040 g / ml or less Δ: Displacement value at 188 ° C .: 500 μm or more and foaming density: more than 0.040 g / ml ×: 188 ° C. Displacement value at: less than 500 μm and foam density: over 0.040 g / ml

[Comparative Example 0: unheat treated product]
When the microsphere (Kureha Co., Ltd., Microsphere, H1100) was used as an unheat-treated product, the foaming start temperature Ts and the maximum foaming temperature Tmax were evaluated by TMA to be 190 ° C. and 208 ° C., respectively.

[Example 1]
Using an extruder (manufactured by Technobel, KZW-15), EMMA (MFR 0.25 g / 10 min, melting temperature 67 ° C.) and microsphere (H1100) were mixed, and the blend ratio was 1: 1 (weight ratio). Extrusion was performed at a screw speed of 100 R / min. The screw temperature at that time was set at 70 ° C. to 90 ° C., and the temperature of the dice (φ2.5 × 2 holes) (heat treatment temperature: T1) was set to 110 ° C. to obtain a sample. The obtained samples were evaluated as described above.

[Example 2]
Samples were prepared and evaluated in the same manner as in Example 1 except that the heat treatment temperature (T1) was 120 ° C.

[Example 3]
Samples were prepared and evaluated in the same manner as in Example 1 except that the heat treatment temperature (T1) was 130 ° C.

[Comparative Example 1]
Samples were prepared and evaluated in the same manner as in Example 1 except that the heat treatment temperature (T1) was 80 ° C.

[Comparative Example 2]
Samples were prepared and evaluated in the same manner as in Example 1 except that the heat treatment temperature (T1) was 90 ° C.

[Comparative Example 3]
Samples were prepared and evaluated in the same manner as in Example 1 except that the heat treatment temperature (T1) was 100 ° C.

* Numbers in parentheses indicate differences from Comparative Example 0.

[Example 4]
A 2.0 g sample of Comparative Example 1 was heat-treated in an oven at 130 ° C. for 5 minutes to produce a heat-treated sample, and this heat-treated sample was evaluated in the same manner as in Example 1.

[Example 5]
A 2.0 g sample of Comparative Example 2 was heat-treated in an oven at 130 ° C. for 5 minutes to produce a heat-treated sample, and this heat-treated sample was evaluated in the same manner as in Example 1.

[Example 6]
A 2.0 g sample of Comparative Example 3 was heat-treated in an oven at 130 ° C. for 5 minutes to produce a heat-treated sample, and this heat-treated sample was evaluated in the same manner as in Example 1.

[Example 7]
A 2.0 g sample of Example 1 was heat-treated in an oven at 130 ° C. for 5 minutes to produce a heat-treated sample. The heat-treated sample was evaluated in the same manner as in Example 1.

[Example 8]
A heat treatment sample was prepared by heating 2.0 g of the sample of Example 2 in an oven at 130 ° C. for 5 minutes, and this heat treatment sample was evaluated in the same manner as in Example 1.

[Example 9]
A 2.0 g sample of Example 3 was heat-treated in an oven at 130 ° C. for 5 minutes to produce a heat-treated sample. The heat-treated sample was evaluated in the same manner as in Example 1.

* Numbers in parentheses indicate differences from Comparative Example 0.

As is apparent from Tables 1 and 2 and FIGS. 1 and 2, according to the production method of the present invention, the foaming start temperature and the maximum foaming temperature are reduced, and the temperature at the time of heating and foaming can be lowered, thereby suppressing the energy cost. It has excellent energy-saving properties and excellent uniformity of foaming behavior, so that the microspheres are uniformly foamed and the foamed state is good, so it has excellent overall productivity. I understand.

Claims

A method for producing a foam molded article,
The method includes a step (A) of obtaining an unfoamed molded article comprising a thermally foamable composition, and a step (B) of heating and foaming the unfoamed molded body at a temperature T2 (° C.).
The thermally foamable composition contains microspheres and at least one substrate selected from the group consisting of thermoplastic resins, thermosetting resins, and fibers,
The microsphere includes an outer shell containing a polymer, and a foaming agent enclosed in the outer shell,
Step (A) includes a step (a) of heat-treating the thermally foamable composition at a temperature T1 (° C.),
The foaming start temperature of the microsphere after the heat treatment in the step (a) is 10 ° C. or more lower than the foaming start temperature of the microsphere before the heat treatment in the step (a),
The maximum foaming temperature of the microsphere after the heat treatment in the step (a) is 5 ° C. or more lower than the maximum foaming temperature of the microsphere before the heat treatment in the step (a),
The temperature T1 and T2 satisfy | fill following formula (1) and (2), respectively, The method characterized by the above-mentioned.
105 ≦ T1 <Ts (° C.) (1)
Ts-40 ≦ T2 <Tmax-3 (° C.) (2)
(In the formula, Ts (° C.) represents the foaming start temperature of the microsphere before heat treatment in step (a), and Tmax (° C.) represents the maximum foaming of the microsphere before heat treatment in step (a). Represents temperature.)
The method according to claim 1, wherein in the step (A), the unfoamed molded article is obtained by molding the thermally foamable composition heat-treated in the step (a).
In the step (A), after molding the thermally foamable composition before the heat treatment in the step (a), the molded foamed composition is heat treated in the step (a), so that the unfoamed molding is performed. The method according to claim 1, wherein a body is obtained.
The method according to any one of claims 1 to 3, wherein the polymer contains a copolymer containing a structural unit derived from (meth) acrylonitrile and a structural unit derived from (meth) acrylic acid ester.