Foamed sheet

Patent metadata

Field	Value
Publication number	US-2016304680-A1
Application number	US-201515101555-A
Country	US
Kind code	A1
Filing date	Sep 18, 2015
Priority date	Sep 24, 2014
Publication date	Oct 20, 2016
Grant date	—

Abstract

There is provided a foamed sheet which takes only a short time to recover the thickness thereof after being compressed, and even if being subjected to repeated impacts, hardly decreases in the impact absorption. The foamed sheet according to the present invention comprises a foamed body formed of a resin composition comprising: a thermoplastic resin a and a silicone-based compound b having not more than 2,000 siloxane bonds; and/or a thermoplastic resin a′ having a silicone chain having not more than 2,000 siloxane bonds. The thermoplastic resin a is preferably at least one selected from the group consisting of acrylic polymers, rubbers, urethanic polymers and ethylene-vinyl acetate copolymers. The silicone-based compound b is preferably at least one selected from the group consisting of silicone oils, modified silicone oils and silicone resins.

First claim

1 . A foamed sheet, comprising a foamed body formed of a resin composition comprising: a thermoplastic resin a and a silicone-based compound b having not more than 2,000 siloxane bonds; and/or a thermoplastic resin a′ having a silicone chain having not more than 2,000 siloxane bonds.

2 . The foamed sheet according to claim 1 , wherein the thermoplastic resin a is at least one selected from the group consisting of acrylic polymers, rubbers, urethanic polymers and ethylene-vinyl acetate copolymers.

3 . The foamed sheet according to claim 1 , wherein the silicone-based compound b is at least one selected from the group consisting of silicone oils, modified silicone oils and silicone resins.

4 . The foamed sheet according to claim 1 , wherein the foamed body has a total content of the silicone-based compound b and a silicone chain moiety present in the thermoplastic resin a′ having a silicone chain of 0.01 to 5 parts by weight in terms of nonvolatile content, with respect to 100 parts by weight of a total amount of the thermoplastic resins in the foamed body.

5 . The foamed sheet according to claim 1 , wherein the foamed body has an apparent density of 0.2 to 0.7 g/cm 3 , and an average cell diameter of 10 to 150 μm.

6 . The foamed sheet according to claim 1 , wherein the foamed sheet has a thickness of 30 to 500 μm.

7 . The foamed sheet according to claim 1 , wherein the foamed sheet has a value R of not less than 0.08, the value R being obtained by dividing an impact absorption rate (%) defined by the following expression by a thickness (μm) of the foamed sheet, in an impact absorption test (a weight of an impactor: 96 g, a swing-up angle: 47°) using a pendulum impact tester:
an impact absorption rate (%)={( F 0 −F 1 )/ F 0 }×100

wherein F 0 is an impact force when the impactor is made to collide with a support plate alone; and F 1 is an impact force when the impactor is made to collide with the support plate of a structural body composed of the support plate and the foamed sheet.

8 . The foamed sheet according to claim 1 , wherein the foamed body is formed through step A of mechanically foaming an emulsion resin composition.

9 . The foamed sheet according to claim 8 , wherein the foamed body is formed further through step B of coating a base material with the mechanically foamed emulsion resin composition followed by drying.

10 . The foamed sheet according to claim 9 , wherein step B comprises preliminary drying step B1 of drying the bubble-containing emulsion resin composition applied on the base material at not less than 50° C. and less than 125° C., and regular drying step B2 of thereafter further drying the resultant at not less than 125° C. and not more than 200° C.

11 . The foamed sheet according to claim 1 , wherein the number of the siloxane bonds in the silicone-based compound b having not more than 2,000 siloxane bonds is not more than 1,000.

12 . The foamed sheet according to claim 4 , wherein the foamed body has a total content of the silicone-based compound b and a silicone chain moiety present in the thermoplastic resin a′ having a silicone chain of 0.05 to 4 parts by weight in terms of nonvolatile content, with respect to 100 parts by weight of the total amount of the thermoplastic resins in the foamed body.

13 . The foamed sheet according to claim 12 , wherein the foamed body has a total content of the silicone-based compound b and a silicone chain moiety present in the thermoplastic resin a′ having a silicone chain of 0.1 to 3 parts by weight in terms of nonvolatile content, with respect to 100 parts by weight of the total amount of the thermoplastic resins in the foamed body.

14 . The foamed sheet according to claim 5 , wherein a foamed body has an apparent density of 0.21 to 0.6 g/cm 3 .

15 . The foamed sheet according to claim 14 , wherein a foamed body has an apparent density of 0.22 to 0.5 g/cm 3 .

16 . The foamed sheet according to claim 1 , wherein the foamed sheet has a pressure-sensitive adhesive layer on one face or both faces of the foamed body.

17 . The foamed sheet according to claim 1 , being used as an impact absorption sheet for an electric or electronic device.

18 . An electric or electronic device, using a foamed sheet according to claim 1 .

19 . An electric or electronic device comprising a display member, a housing, and the foamed sheet according to claim 1 interposed between the housing of the electric or electronic device and the display member.

Assignees

• Nitto Denko Corp

Inventors

• Doi Kohei
• Kato Kazumichi
• Tokuyama Hideyuki
• Takahashi Tadao

Classifications

• B32B2307/306

  Resistant to heat · CPC title

• C09J175/04

  Polyurethanes · CPC title

• C08J2207/00

  Foams characterised by their intended use · CPC title

• C08J9/0061

  characterized by the use of several polymeric components · CPC title

• C08J9/30

  by mixing gases into liquid compositions or plastisols, e.g. frothing with air · CPC title