Foamed sheet

Patent metadata

Field	Value
Publication number	US-10316156-B2
Application number	US-201515101555-A
Country	US
Kind code	B2
Filing date	Sep 18, 2015
Priority date	Sep 24, 2014
Publication date	Jun 11, 2019
Grant date	Jun 11, 2019

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

The invention claimed is:

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,
wherein the thermoplastic resin a is at least one selected from the group consisting of acrylic polymers, rubbers, and ethylene-vinyl acetate copolymers,
wherein the resin composition does not include an urethanic polymer,
wherein the silicone-based compound b is an unmodified silicone oil,
wherein the acrylic polymer is formed from 2 to 30% by weight of a monomer whose homopolymer has a glass transition temperature of not less than −10° C. and 70 to 98% by weight of a monomer whose homopolymer has a glass transition temperature of less than −10° C.,
wherein the foamed body has an apparent density of 0.21 to 0.7 g/cm 3 , and an average cell diameter of 15 to 150 μm,
wherein a ratio of the average cell diameter to a thickness of the foamed body is in the range of 0.2 to 0.9,
wherein the foamed body has a content of the silicone-based compound b of 0.01 to 5 parts by weight in terms of nonvolatile content, with respect to 100 parts by weight of the thermoplastic resin a in the foamed body, and
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.

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

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

4. The foamed sheet according to claim 3 , 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.

5. The foamed sheet according to claim 4 , wherein step B comprises preliminary drying step B 1 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 B 2 of thereafter further drying the resultant at not less than 125° C. and not more than 200° C.

6. 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.

7. The foamed sheet according to claim 1 , wherein the foamed body has a content of the silicone-based compound b of 0.05 to 4 parts by weight in terms of nonvolatile content, with respect to 100 parts by weight of the thermoplastic resin a in the foamed body.

8. The foamed sheet according to claim 7 , wherein the foamed body has a content of the silicone-based compound b of 0.1 to 3 parts by weight in terms of nonvolatile content, with respect to 100 parts by weight of the thermoplastic resin a in the foamed body.

9. The foamed sheet according to claim 1 , wherein a foamed body has an apparent density of 0.21 to 0.6 g/cm 3 .

10. The foamed sheet according to claim 9 , wherein a foamed body has an apparent density of 0.22 to 0.5 g/cm 3 .

11. 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.

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

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

14. 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.

15. The foamed sheet according to claim 1 , wherein a cell structure of the foamed body is an open cell structure or a semi-open semi-closed cell structure.

16. The foamed sheet according to claim 1 , wherein the foamed body comprises a fatty acid ammonium-based surfactant.

17. The foamed sheet according to claim 1 , wherein the foamed body comprises an oxazoline-based crosslinking agent.

18. The foamed sheet according to claim 1 , wherein the foamed body comprises an azole ring-containing compound as a rust preventative.

Assignees

• Nitto Denko Corp

Inventors

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

Classifications

• C08J2333/06

  of esters containing only carbon, hydrogen, and oxygen, the oxygen atom being present only as part of the carboxyl radical · CPC title

• C09J123/0853

  Vinylacetate · CPC title

• C08J2433/08

  Homopolymers or copolymers of acrylic acid esters · CPC title

• C09J2433/006

  in the substrate · CPC title

• B32B2307/306

  Resistant to heat · CPC title