Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-09-13
2001-05-22
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S054000, C521S056000, C521S060000
Reexamination Certificate
active
06235800
ABSTRACT:
TECHNICAL FIELD
The present invention relates to thermo-expandable microcapsules having superior thermo-resistance and the application thereof.
TECHNICAL BACKGROUND
The production process of thermo-expandable microcapsules wherein thermoplastic polymer encapsulates a volatile expansion agent which gasifies at a temperature lower than the softening point of the polymer has already been disclosed, for example, in Japanese Patent Publication Sho 42-26524.
Japanese Patent Laid-Open Sho 60-19033 (equivalent to U.S. Pat. No. 4,582,756) discloses a process wherein the surface of micro-balloons is covered with thermosetting resin to produce solvent-resistant micro-balloons that can be added into hot molten resin.
Japanese Patent Publication Hei 5-15499 and Japanese Patent Laid-Open Hei 5-285376 (equivalent to U.S. Pat. No. 5,536,756) disclose a process wherein a monomer mixture comprising 80 percent or more of nitrile monomer having polymerizable unsaturated bonds form the shell of microcapsules that have superior heat and solvent resistance.
The microcapsules produced in the processes are blended in synthetic resins to impart matte and bulky effect to construction materials (materials for ceiling, wall, floor and the like) or coating materials for bags.
Japanese Patent Laid-Open Hei 7-304968 (equivalent to U.S. Pat. No. 5,726,222) discloses the microcapsules comprising a shell of which main component is (B) a thermoplastic resin soluble in a thermosetting resin under heating and (A) a curing agent of the thermosetting resin being encapsulated in the shell. It discloses that the microcapsules contribute to the production of a thermosetting resin composition or prepreg stable under storage at normal temperature and fiber-reinforced composite having uniform hardness and superior mechanical property. And polyether imide and polyimide are exemplified as the thermoplastic resin, (B), and maleimide resin is exemplified as the thermosetting resin.
Microcapsules need to be heated for expansion and their color changes depending on the heating temperature, remarkably at 200° C. or more. None of the thermo-expandable microcapsules developed in the past as mentioned above was durable against the color change under heating at 200° C. or more and retained matte effect.
The object of the present invention is to provide thermo-expandable microcapsules which can be used to produce synthetic resin foam layer having matte and bulky surface and durable against thermal coloration especially under heating at 200° C. or more and to provide resin foam and foamed resin composite produced with the same to solve the above problem.
DISCLOSURE OF INVENTION
The present invention provides the products and processes described from (1) to (6) as follows.
(1) A thermo-expandable microcapsule comprising: a shell of a polymer of which main polymerizable monomer components are a nitrile monomer and N-substituted maleimide; and a volatile expanding agent having a boiling point lower than the softening point of the shell polymer, the volatile expanding agent being encapsulated in the shell.
(2) A thermo-expandable microcapsule comprising: a shell of a polymer of which main polymerizable monomer components are a nitrile monomer and N-substituted maleimide and another component is a monomer forming a homopolymer having a Tg of 50-200° C.; and a volatile expanding agent having a boiling point lower than the softening point of the shell polymer, the volatile expanding agent being encapsulated in the shell.
(3) A thermo-expandable microcapsule comprising: a shell of a polymer of which main polymerizable monomer components are a nitrile monomer and N-substituted maleimide and other components are a monomer forming a homopolymer having a Tg of 50-200° C. and polymerizable unsaturated carboxylic acid (including anhydrides); and a volatile expanding agent having a boiling point lower than the softening point of the shell polymer, the volatile expanding agent being encapsulated in the shell.
(4) A thermo-expandable microcapsule described in the above (1) wherein the nitrile monomer contains at least acrylonitrile.
(5) A production process of foamed resin composite produced by coating a base material with a mixture of resin and one of the thermo-expandable microcapsules described in the above (1) to (3) and by heating to form a foamed resin layer.
(6) A production process of resin foam produced by mixing one of the thermo-expandable microcapsules described in the above (1) to (3) and resin and by heating the mixture to form into resin foam.
BEST MODE OF EMBODIMENT OF INVENTION
The best mode of the embodiment of the present invention is described as follows.
The shell of the thermo-expandable microcapsules of the present invention comprises a polymer of which main polymerizable monomer components are nitrile monomer and N-substituted maleimide and another polymerizable monomer component is a monomer forming a homopolymer having 50-200° C. Tg and encapsulates a volatile expanding agent having a boiling point lower than the softening point of the shell polymer.
The preferable polymer for the shell comprises acrylonitrile and N-maleimide as the main polymerizable monomers, a monomer forming a homopolymer having 50-200° C. Tg and polymerizable unsaturated carboxylic acids (including anhydrides).
The production process of the foamed resin composite of the present invention comprises the step wherein a base material is coated with the mixture of the thermo-expandable microcapsules and resin and heated to be formed into foamed resin layer.
The production process of the foam of the present invention comprises the step wherein the thermo-expandable microcapsules and resin are mixed and heated to be formed into resin foam.
The N-substituted maleimide used for the present invention includes N-phenyl maleimide, N-naphthyl maleimide, N-cycroheyxl maleimide and methyl maleimide, and one or more of halogen atoms can substitute the allyls and alkyls in their molecules. Among those malemimdes, N-phenyl maleimide and N-cyclohexyl maleimide are preferable for their availability.
The ratio of N-substituted maleimide used as the polymerizable monomer for the present invention is 5 to 50 weight percent, preferably 10 to 30 weight percent. The ratio less than 5 weight percent is not effective to prevent the thermal coloring of microcapsules and the ratio more than 50 weight percent fails to produce thermo-expandable microcapsules having sufficient expanding performance.
The polymerizable nitrile monomers used for the present invention are acrylonitrile, methacrylonitrile and dicyanonitrile. Among those, acrylonitrile, being blended by 40 to 85 weight percent of the shell polymer, is preferable for attaining high heat resistance and vapor-barrier performance.
The ratio of nitrile monomer in the polymerizable monomers for forming the shell is 55 to 85 weight percent. The ratio less than 55 weight percent causes low vapor-barrier performance, while the ratio more than 85 weight percent results in poor expansion of microcapsules.
The polymerizable monomer used for the present invention other than acrylonitrile and N-substituted maleimide is selected among the monomers of which homopolymer has a Tg of 50 to 200° C. The examples of such monomers are acrylate, methacrylate and styrene.
The ratio of those monomers is usually 25 weight percent or less, preferably 5 to 25 weight percent. The ratio higher than 25 weight percent reduces gas-barrier performance or expansion performance of microcapsules.
The polymerizable unsaturated carboxylic acids (including anhydrides) used for the present invention include acrylic acid, methacrylic acid, crotonic acid, maleic acid and maleic anhydride. And methacrylic acid, crotonic acid and maleic anhydride are preferable for attaining high foaming performance.
The ratio of those carboxylic acids is usually 5 weight percent or less, preferably 0.1 to 3 weight percent. The ratio more than 5 weight percent reduces the expansion performance of microcapsules.
The volatile expansion agent having a boiling point lower than the softening
Kyuno Seiji
Masuda Toshiaki
Foelak Morton
Foley & Lardner
Matsumoto Yushi-Seiyaku Co. Ltd.
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