Polyamide resin composition, expanded polyamide resin molding, and automotive resin molding

• US 9,447,575 B2
• Filed: 11/01/2011
• Issued: 09/20/2016
• Est. Priority Date: 11/01/2010
• Status: Active Grant

• Current Assignee: Toyobo MC Corp.
• Original Assignee: Toyobo Company Limited
• Inventors: Ohashi, Tadamine, Fujii, Yasuto, Tange, Akio, Nakagawa, Tomohide
• Primary Examiner(s): Zemel, Irina S
• Application Number:
  US13/880,169
• Publication Number:
  US 20130209784A1
• Time in Patent Office: 1,785 Days
• US Class Current: 1/1
• CPC Class Codes: B29C 44/02 for articles of definite length, i.e. discrete articles
• CPC Class Codes: C08J 2377/00 Characterised by the use of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Derivatives of such polymers
• CPC Class Codes: C08J 9/06 by a chemical blowing agent
• CPC Class Codes: C08K 3/013 Fillers, pigments or reinforcing additives
• CPC Class Codes: C08L 2205/02 containing two or more polymers of the same C08L -group
• CPC Class Codes: C08L 25/04 Homopolymers or copolymers of styrene
• CPC Class Codes: C08L 77/00 Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain of polyhydrazides C08L79/06; of polyamideimides or polyamide acids C08L79/08; Compositions of derivatives of such polymers
• CPC Class Codes: E04B 1/78 Heat insulating elements E04B1/7662 takes precedence
• CPC Class Codes: F02F 7/0085 Materials for constructing engines or their parts
• CPC Class Codes: Y10T 428/249977 Specified thickness of void-containing component [absolute or relative], numerical cell dimension or density

Abstract

Provided is a polyamide resin composition which can provide an expanded molding being superior in heat resistance and sufficiently reduced in weight and having high load resistance by a simple molding process. The polyamide resin composition is characterized by comprising a polyamide resin (A), a glycidyl-group-containing styrene copolymer (B) having two or more glycidyl groups per molecule, a weight average molecular weight of 4000 to 25000 and an epoxy value of 400 to 2500 Eq/1×10⁶ g and an inorganic reinforcing material (C) in a proportion such that the content of the glycidyl-group-containing styrene copolymer (B) is 0.2 to 25 parts by mass and the content of the inorganic reinforcing material (C) is 0 to 350 parts by mass relative to 100 parts by mass of the polyamide resin (A).

Claims

1. An expanded polyamide resin molding obtained by using a polyamide resin composition comprising:

a polyamide resin (A);

a glycidyl group-containing styrene copolymer (B) having two or more glycidyl groups per molecule, a weight average molecular weight of 4000 to 25000, and an epoxy value of 400 to 2500 Eq/1×

10⁶ g; and

an inorganic reinforcing material (C) in a proportion such that the content of the glycidyl group-containing styrene copolymer (B) is 0.2 to 25 parts by mass and the content of the inorganic reinforcing material (C) is 0 to 350 parts by mass relative to 100 parts by mass of the polyamide resin (A),

wherein the expanded polyamide resin molding comprises an expanded layer comprising a continuous resin phase and closed foam cells, and an unexpanded skin layer on the expanded layer, and

wherein the expanded layer has an average cell diameter of 300 μ

m or shorter and has no voids having a length continuity of 800 μ

m or longer.

2. The expanded polyamide resin molding according to claim 1, wherein the polyamide resin (A) comprises a crystalline polyamide resin (a) and a noncrystalline polyamide resin (b), the proportion of which is (a):

(b)=0 to 100;

100 to 0 (mass ratio).

3. The expanded polyamide resin molding according to claim 1, wherein the glycidyl group-containing styrene copolymer (B) is a copolymer including 20 to 99% by mass of a vinyl aromatic monomer (X), 1 to 80% by mass of a glycidylalkyl (meth)acrylate (Y), and 0 to 79% by mass of a vinyl group-containing monomer (Z) containing no epoxy group other than the (X).

4. The expanded polyamide resin molding according to claim 1, wherein a matrix composition comprising the polyamide resin (A) and the glycidyl group-containing styrene copolymer (B) has an α

of smaller than 1.4 and an absolute value of (α

−

β

) of 0.5 or less, where a multiplier (y=ax^α

;

a is a constant) taken when a storage modulus (unit;

Pa) obtained by melt viscoelasticity measurement within a frequency range of 10 to 100 rad/s in a linear region is plotted on a log-log graph of a frequency (x) and a storage modulus (y) is represented by α

, and a multiplier (y′

=bx′

^β

;

b is a constant) taken when a loss modulus (unit;

Pa) obtained by melt viscoelasticity measurement within a frequency range of 10 to 100 rad/s in a linear region is plotted on a log-log graph of a frequency (x′

) and a loss modulus (y′

) is represented by β

.

5. The expanded polyamide resin molding according to claim 1 obtained by injecting and filling the polyamide resin composition in a molten state together with a supercritical inert gas into a cavity formed by two or more molds closed, and then enlarging the capacity of the cavity by moving at least one of the molds in the mold opening direction at a stage where an unexpanded skin layer being 100 to 800 μ

m in thickness is formed in a surface layer.

14. The expanded polyamide resin molding according to claim 1, wherein the expanded layer comprising the continuous resin phase and closed foam cells having an average cell diameter of 10 to 300 μ

m and the unexpanded skin layer stacked on the expanded layer and having a thickness of 100 to 800 μ

m are formed of the polyamide resin composition, and the expanded polyamide resin molding has a specific gravity of 0.2 to 1.0.

15. The expanded polyamide resin molding according to claim 14, having a sandwich structure in which the unexpanded layers are provided on both sides of the expanded layer.

6. An expanded polyamide resin molding obtained by bringing a polyamide resin composition into a molten state, injecting and filling the polyamide resin composition together with a supercritical inert gas into a cavity formed by two or more molds closed, and then enlarging the capacity of the cavity by moving at least one of the molds in the mold opening direction at a stage where an unexpanded skin layer being 100 to 800 μ

m in thickness is formed in a surface layer, wherein

the polyamide resin composition comprises;

a crystalline polyamide resin (a);

a noncrystalline polyamide resin (b);

a glycidyl group-containing styrene copolymer (B) having two or more glycidyl groups per molecule, a weight average molecular weight of 4000 to 25000, and an epoxy value of 400 to 2500 Eq/1×

10⁶ g; and

an inorganic reinforcing material (C) in a proportion such that the content of the glycidyl group-containing styrene copolymer (B) is 0 to 30 parts by mass and the content of the inorganic reinforcing material (C) is 0 to 350 parts by mass relative to 100 parts by mass of the crystalline polyamide resin (a) and the noncrystalline polyamide resin (b) in total,

the expanded polyamide resin molding comprises an expanded layer comprising a continuous resin phase and closed foam cells and an unexpanded skin layer on the expanded layer, and

the expanded layer has the average cell diameter of 300 μ

m or shorter and has no voids having a length continuity of 800 μ

m or longer.

7. The expanded polyamide resin molding according to claim 6, wherein the proportion of the crystalline polyamide resin (a) and the noncrystalline polyamide resin (b) is the crystalline polyamide-resin (a):

the noncrystalline polyamide resin (b)=95;

5 to 50;

50 (mass ratio).

8. The expanded polyamide resin molding according to claim 6, wherein the glycidyl group-containing styrene copolymer (B) is a copolymer including 20 to 99% by mass of a vinyl aromatic monomer (X), 1 to 80% by mass of a glycidylalkyl (meth)acrylate (Y), and 0 to 79% by mass of a vinyl group-containing monomer (Z) containing no epoxy group other than the (X).

9. The expanded polyamide resin molding according to claim 6, wherein the resonant frequency, x (Hz), of the expanded polyamide resin molding is 1.5 times or more the resonant frequency, y(Hz), of an unexpanded molding obtained by bringing the polyamide resin composition into a molten state, injecting the polyamide resin composition into a cavity formed by two or more molds closed without pouring any supercritical inert gas, and molding the polyamide resin composition without moving any mold in the mold opening direction.

10. The expanded polyamide resin molding according to claim 6, wherein the expanded layer composed of the continuous resin phase and closed foam cells having an average cell diameter of 10 to 300 μ

m and the unexpanded skin layer stacked on the expanded layer and having a thickness of 100 to 800 μ

m are formed of the polyamide resin composition, and the expanded polyamide resin molding has a specific gravity of 0.2 to 1.0.

11. The expanded polyamide resin molding according to claim 10, having a sandwich structure in which the unexpanded layers are provided on both sides of the expanded layer.

12. An automotive resin molding having a heat insulating property, which is formed of the expanded polyamide resin molding according to claim 6.

13. The automotive resin molding having a heat insulating property according to claim 12, which is a thermally resistant cover selected from the group consisting of an engine cover, a cylinder head cover, and a transmission cover.