Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-03-28
2002-06-04
Foelak, Morton (Department: 1911)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C264S050000, C264S051000, C264S053000, C264S045900, C521S079000
Reexamination Certificate
active
06399667
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing a foamed resin article and the like, particularly to a process for producing a foamed resin article having fine cells in a high cell density and the like.
2. Description of the Related Art
In recent years, a supercritical foaming technique wherein a foamed resin article having fine cells in a high cell density is produced by using an inert substance (carbon dioxide, nitrogen and the like) in a supercritical state has been developed [see, for example, Material & Manufacturing Process, 4 (2), 253-262 (1989) and U.S. Pat. No. 5,160,674]. Development of techniques by which higher cell densities can be achieved is still required, however.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a process for producing a foamed resin article having fine cells in a higher cell density, and the like.
The present inventors have studied intensively on a process for producing a foamed resin article having fine cells in a higher cell density, and as a result, have found a process for producing a foamed resin article comprising two steps using a specific resin material can attain the above object and have accomplished the present invention.
That is, the present invention provides:
1. a process for producing a foamed resin article, the process comprising:
a step (the first step) of impregnating any one crystalline thermoplastic resin or resin composition containing, as an elementary ingredient, a crystalline thermoplastic resin selected from ones listed below, under an elevated pressure which is not lower than the critical pressure of a substance with which the selected crystalline thermoplastic resin or resin composition is to be impregnated, with a fluid of the substance, and
a step (the second step) of releasing the resin or resin composition impregnated with the substance from the foregoing pressurized condition in a period of less than 10 seconds. (Hereinafter, it may sometimes be referred to as the process of the present invention.)
(Crystalline Thermoplastic Resin or Resin Composition Containing, as an Elementary Ingredient, a Crystalline Thermoplastic Resin)
(a) A polypropylene resin which is a crystalline thermoplastic resin
(b) A resin composition comprising not less than 50% by weight of a polypropylene resin which is a crystalline thermoplastic resin, as an elementary ingredient
(c) A resin composition comprising 60 to 90 parts by weight of a crystalline thermoplastic resin as an elementary ingredient and 10 to 40 parts by weight of a non-crystalline thermoplastic resin
(d) A crystalline thermoplastic resin or a crystalline thermoplastic resin composition wherein an endothermic curve obtained by measurement at a rate of heating of 10° C./min using a differential scanning calorimeter (DSC) has at least one endothermic peak and wherein when taking the highest peak point among the at least one endothermic peak as A, taking the point appearing on the higher temperature side at which the minimum endothermic heat value is given as F, taking the point at which a straight line (a base line) which passes through the point F and is parallel to the temperature axis intersects a perpendicular dropped from the point A to the temperature axis as B, taking the point which internally divides the segment AB in the perpendicular into 9:1 as C, taking the point at which a straight line which passes through the point C and is parallel to the temperature axis intersects the endothermic curve at the lowest temperature as D, and taking the point at which the line CD intersects the endothermic curve at the highest temperature as E, a difference in temperature indicated by the length of the segment DE is 20° C. or more.
2. the process for producing a foamed resin article according to the above 1, wherein the release from the pressurized condition in the second step is conducted in a period of 3 seconds or shorter.
3. the process for producing a foamed resin article according to the above 1, wherein the second step is conducted at a lower temperature than a temperature at which the first step is conducted.
4. the process for producing a foamed resin article according to the above 1, wherein the release from the pressurized condition in the second step is conducted at a lower temperature than a melting point of the resin or resin composition used.
5. the process for producing a foamed resin article according to the above 1, wherein the impregnation in the first step is conducted under the pressurized conditions of at a temperature of 300° C. or lower, in a period of 5 hours or shorter and at a pressure of 10 MPa or higher.
6. the process for producing a foamed resin article according to the above 1, wherein the impregnation in the first step is conducted under the pressurized conditions of at a temperature in the range of 60 to 230° C., in a period of 3 hours or shorter and at a pressure in the range of 10 to 50 MPa.
7. the process for producing a foamed resin article according to the above 1, wherein the crystalline thermoplastic resin is a polypropylene resin, which is a crystalline thermoplastic resin. (Hereinafter, it may sometimes be referred to as the process A of the present invention.)
8. the process for producing a foamed resin article according to the above 1, wherein the resin composition is a resin composition comprising not less than 50% by weight of a polypropylene resin which is a crystalline thermoplastic resin, as an elementary ingredient. (Hereinafter, it may sometimes be referred to as the process A′ of the present invention.)
9. the process for producing a foamed resin article according to the above 1, wherein the resin composition is a resin composition comprising 60 to 90 parts by weight of a crystalline thermoplastic resin as an elementary ingredient and 10 to 40 parts by weight of a non-crystalline thermoplastic resin. (Hereinafter, it may sometimes be referred to as the process B of the present invention.)
10. the process for producing a foamed resin article according to the above 9, wherein the resin composition comprises a crystal phase and a non-crystal phase and the size of the non-crystal phase is 10 to 200 nm.
11. the process for producing a foamed resin article according to the above 1, wherein the crystalline thermoplastic resin or the resin composition is a crystalline thermoplastic resin or a crystalline thermoplastic resin composition wherein an endothermic curve obtained by measurement at a rate of heating of 10° C./min using a differential scanning calorimeter (DSC) has at least one endothermic peak and wherein when taking the highest peak point among the at least one endothermic peak as A, taking the point appearing on the higher temperature side at which the minimum endothermic heat value is given as F, taking the point at which a straight line (a base line) which passes through the point F and is parallel to the temperature axis intersects a perpendicular dropped from the point A to the temperature axis as B, taking the point which internally divides the segment AB in the perpendicular into 9:1 as C, taking the point at which a straight line which passes through the point C and is parallel to the temperature axis intersects the endothermic curve at the lowest temperature as D, and taking the point at which the line CD intersects the endothermic curve at the highest temperature as E, a difference in temperature indicated by the length of the segment DE is 20° C. or more. (Hereinafter, it may sometimes be referred to as the process C of the present invention.)
12. A foamed resin article produced by the process of the above 1. (Hereinafter, it may sometimes be referred to as the foamed resin article of the present invention.)
13. A foamed resin article characterized by being formed of a polypropylene resin which is a crystalline thermoplastic resin, or a resin composition comprising not less than 50% by weight of a polypropylene resin which is a crystalline thermoplastic resin, and by having an average cell density of not le
Kuroda Ryuma
Nodono Mitsunori
Fitch Even Tabin & Flannery
Foelak Morton
Sumitomo Chemical Company Limited
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