Process for preparing open-cell sponge rubber printing material having small and large interconnected cells

• US 4,212,839 A
• Filed: 11/10/1977
• Issued: 07/15/1980
• Est. Priority Date: 11/12/1976
• Status: Expired due to Term

• Current Assignee: Shachihata Industrial Company Limited
• Original Assignee: Takaji Funahashi
• Inventors: Funahashi, Takaji
• Primary Examiner(s): Anderson, Philip
• Application Number:
  US05/850,452
• Time in Patent Office: 978 Days
• Field of Search: 264/49, 264/45.3, 521/61, 101/333, 101/401.1
• US Class Current: 264/45.3
• CPC Class Codes: B41K 1/34 for multicolour stamping
• CPC Class Codes: B41N 1/12 non-metallic other than stone , e.g. printing plates or foils comprising inorganic materials in an organic matrix B41N1/003, B41N1/006 take precedence
• CPC Class Codes: C08J 2201/0444 Salts
• CPC Class Codes: C08J 2201/046 Elimination of a polymeric phase
• CPC Class Codes: C08J 2321/00 Characterised by the use of unspecified rubbers
• CPC Class Codes: C08J 9/26 by elimination of a solid phase from a macromolecular composition or article, e.g. leaching out

Abstract

A printing material composed of an open-cell sponge rubber capable of including therein a colored ink, which does not necessitate a stamp pad for the stamping operation, is disclosed. This printing material is prepared by adding appropriate amounts of soluble starch and a fine powder of an easily water-soluble salt which does not decompose or gasify at a curing temperature to a mixture of a starting rubber, a curing agent and a filler, kneading and milling the mixture, introducing the mixture into a mold, heating the mixture to effect curing, removing said starch and salt by washing, and drying the resulting product.

Claims

1. In process for preparing a sponge rubber printing material having numerous open cells which comprises mixing a starting rubber material, a curing agent, a filler and a material for forming cells, introducing the resulting mixture into a mold, heating the mixture to effect curing and then washing the cured product to remove cell formers, the improvement comprising using a combination of a finely divided soluble starch having a particle size within the range of from 0.01 to 0.103 mm to form small open cells (a) and a fine powder of a readily water-soluble salt selected from the group consisting of sodium chloride, sodium sulfate, sodium nitrate, and mixtures thereof, having a particle size within the range of from 0.149 to 0.498 mm to form large open cells (b) as the material for forming cells, the amount of the starch being 200 to 1200 parts by weight of the starting rubber and the ratio of the amount of starch to readily water-soluble salt being in the range of from 1:

9 to 1;

3, whereby the said small and large open cells (a) and (b) are uniformly distributed throughout the rubber substrate in a state wherein said small and large open cells (a) and (b) are interconnected with one another through interconnecting passages free from obstruction.

2. A process for the preparation of sponge rubber printing materials according to claim 1 wherein the starting rubber is a butadiene-acrylonitrile copolymer.

3. In a process for preparing a sponge rubber printing material having numerous open cells which comprises separately forming two different raw rubber sheet compositions by kneading and milling a mixture containing a starting rubber, a curing agent, a filler, and a material for forming open cells, molding the resulting two sheets in a tightly superposed state, curing the superposed sheets, and washing the cured product to remove the materials for forming open cells, the improvement comprising using a combination of a soluble starch and fine powder of a readily water-soluble salt selected from the group consisting of sodium chloride, sodium sulfate, sodium nitrate and mixtures thereof, the amount of the starch being 200 to 1200 parts by weight of the starting rubber, the ratio of the amount of starch to the water-soluble salt being in a range of from about 1:

9 to 1;

3, and the particle size of said salt and said starch being from about 0.01 to 0.103 mm for one of the sheets, and being from about 0.149 to 0.498 mm for the other of the sheets.