Processes for in-mold coating using a multi-cavity mold and substrates coated thereby

Patent metadata

Field	Value
Publication number	US-10160142-B2
Application number	US-201515504768-A
Country	US
Kind code	B2
Filing date	Aug 12, 2015
Priority date	Aug 22, 2014
Publication date	Dec 25, 2018
Grant date	Dec 25, 2018

Abstract

Disclosed are processes for in-mold coating of a plastic substrate. The processes include: (a) molding a plastic substrate in a first mold cavity of a mold comprising at least two cavities to form a molded plastic substrate; (b) introducing the molded plastic substrate into a second mold cavity of the mold; (c) introducing a coating composition into the second mold cavity containing the molded plastic substrate in order to coat the substrate, the coating composition comprising: (i) a polymer comprising isocyanate-reactive groups; and (ii) a polyisocyanate; (d) curing the composition in the second mold cavity; and (e) opening the mold cavity.

First claim

What is claimed is:

1. A process for in-mold coating comprising:
(a) molding a plastic substrate in a first mold cavity of a mold comprising at least two cavities to form a molded plastic substrate;
(b) introducing the molded plastic substrate into a second mold cavity of the mold;
(c) introducing a coating composition into the second mold cavity containing the molded plastic substrate in order to coat the substrate, the coating composition comprising:
(i) a polymer comprising isocyanate-reactive groups; and
(ii) a polyisocyanate;

(d) curing the composition in the second mold cavity at cure conditions of a mold temperature of 62-105° C. and an external mold pressure of at least 100 kg/mm 2 for a period of at least 60 seconds; and
(e) opening the mold cavity, wherein the coated molded substrate release from the second mold cavity by gravity alone or with suction alone.

2. The process of claim 1 , wherein the substrate comprises a polycarbonate/acrylonitrile butadiene styrene (PC/ABS) blend.

3. The process of claim 1 , wherein the molding of the substrate in the first mold cavity is conducted in the presence of a silicone comprising isocyanate-reactive functional groups.

4. The process of claim 1 , wherein the coating composition is a 100% solids composition.

5. The process of claim 1 , wherein the polymer comprising isocyanate-reactive groups comprises: (i) an aromatic branched polyester polyol; and (ii) an aliphatic polycarbonate polyol.

6. The process of claim 5 , wherein the aromatic branched polyester polyol has a M n of 400 to 1000 gram/mole, a hydroxyl functionality of 1.9 to 2.5, a viscosity at 23° C. of 3000 to 5000 mPa·s, when measured according to DIN EN ISO 3219/A3 determined using a rotational viscometer—Visco Tester® 550, Thermo Haake GmbH, a hydroxyl content of 15.4-16.6% measured according to DIN 53 240/2, and a hydroxyl number of 100 to 200 mg KOH/gram.

7. The process of claim 5 , wherein the weight ratio of (i) and (ii) in the coating composition is in the range of 1:4 to 4:1.

8. The process of claim 1 , wherein the polyisocyanate comprises an isocyanurate of hexamethylene diisocyanate.

9. The process of claim 8 , wherein the polyisocyanate has a viscosity at 23° C. and at 100% solids of 800 to 1400 mPa·s, when measured according to DIN EN ISO 3219/A3 determined using a rotational viscometer—Visco Tester® 550, Thermo Haake GmbH; an isocyanate group content of 22.5-23.5% according to DIN EN ISO 11909; an NCO calculated functionality of 2.8 to 3.2; and a content of monomeric diisocyanate of less than 1 wt. %.

10. The process of claim 1 , wherein the polymer comprising isocyanate-reactive groups and the polyisocyanate are combined in relative amounts such that the coating composition has a ratio of isocyanate groups to isocyanate-reactive groups of 1:1 to 1.8:1.

11. The process of claim 10 , wherein the ratio is at least 1.3:1.

12. The process of claim 1 , wherein the composition further comprises a polyether-modified silicone present in the composition in an amount of 0.1 to 1.0 percent by weight, based on the total weight of the coating composition.

13. The process of claim 1 , wherein the composition further comprises a silicone that is present in the composition in an amount sufficient to provide a cured coating with a surface tension of no more than 30 dynes/cm.

14. The process of claim 1 , wherein an external release agent is present on a surface of the second mold cavity, wherein the external release agent comprises a coating comprising electroless nickel and polytetrafluoroethylene.

15. The process of claim 1 , wherein the coating is cured:
(a) at a mold temperature of 75 to 105° C.,
(b) an external mold pressure of at least 110 (10787 bar); and
(c) for a period of at least at least 70 seconds.

Assignees

• Covestro Llc

Inventors

• Wade Robert A
• Best Kurt E
• Mccanna Jessee

Classifications

• C08G18/44

  Polycarbonates · CPC title

• B29C37/0028 Primary

  In-mould coating, e.g. by introducing the coating material into the mould after forming the article · CPC title

• C08G18/246

  containing also tin-carbon bonds · CPC title

• C08G18/4211

  derived from aromatic dicarboxylic acids and dialcohols · CPC title

• B29C67/246

  Moulding high reactive monomers or prepolymers, e.g. by reaction injection moulding [RIM], liquid injection moulding [LIM] (casting monomers B29C39/006, mixing construction B29B7/74) · CPC title