Primer compositions for injection molding

Abstract

A curable primer composition comprising:(a) a curable component such as methacrylate; (b) a cure initiating component; and (c) a polymer material selected from the group consisting of: (i) block polymers represented by S-A-S where S is polystyrene and A stands for a polymer or copolymer formed from one or more of ethylene, propylene, butylene, and styrene, which are optionally substituted with carboxylic acid or maleic anhydride; provided that when A comprises styrene then A is a copolymer of styrene with at least one of ethylene, propylene and butylene, and is optionally substituted with carboxylic acid or maleic anhydride; and (ii) polystyrene-poly(ethylene-propylene) (“SEP”); and (iii) any combination of said polymer materials. The composition is applied to a part then photocured. It is dry to touch. Thereafter a thermoplastic material such as a polyolefin is overmolded (e.g. injection molded) over the applied composition. It enhances bond strength of the polyolefin to the part.

Claims

1. A process for forming an injection molding about an article, comprising the steps of (a) disposing into an injection molding cavity an article about which a thermoplastic, plastic material is to be molded into a shape; and (b) injecting into the injection molding cavity in which is disposed the article, the thermoplastic material at a temperature and pressure to permit the material to flow around and about the article in the mold and maintaining the mold under a temperature and pressure appropriate to permit the thermoplastic material to solidify, wherein prior to disposition of the article, the article is primed with a curable primer composition of (a) a curable (meth)acrylate component; (b) a cure initiating component; and (c) a polymer material selected from the group consisting of: i. block polymers represented by S-A-S wherein S is polystyrene and A stands for a polymer or copolymer formed from one or more of ethylene, propylene, butylene and styrene, which are optionally substituted with carboxylic acid or maleic anhydride; provided that when A comprises styrene then A is a copolymer of styrene with at least one of ethylene, propylene and butylene, and is optionally substituted with carboxylic acid or maleic anhydride; and ii. polystyrene-poly(ethylene-propylene) (“SEP”); and iii. any combination of said polymer materials and exposed to radiation in the electromagnetic spectrum appropriate to cure the composition, wherein the polymer material comprises about 10 to about 70 weight percent styrene based on the total weight of the polymer material.

2. The process of claim 1, wherein the article is constructed from glass.

3. The process of claim 1, wherein the article is constructed from aluminium.

4. The process of claim 1, wherein the article is constructed from anodized aluminium.

5. The process of claim 1, wherein the polymer material is selected from the group consisting of block polymers represented by S-A-S where S is polystyrene and A stands for a polymer or copolymer formed from one or more of ethylene, propylene, butylene and styrene which are optionally substituted with carboxylic acid or maleic anhydride; provided that when A comprises styrene then A is a copolymer of styrene with at least one of ethylene, propylene and butylene, and is optionally substituted with carboxylic acid or maleic anhydride; and any combination of said polymer materials.

6. The process of claim 1, wherein A is formed from one or more of ethylene, propylene, butylene and styrene, provided that A is not formed from styrene alone.

7. The process of claim 1, wherein A is formed from at least two of ethylene, propylene, butylene and styrene.

8. The process of claim 1, wherein A is formed from at least three of ethylene, propylene, butylene and styrene.

9. The process of claim 1, wherein the material S-A-S is selected from: a. polystyrene-poly(ethylene-propylene)-polystyrene (“SEPS”); b. polystyrene-poly(ethylene-butylene)-polystyrene (“SEBS”); and c. polystyrene-poly(ethylene-butylene-styrene)-polystyrene (“S(EBS)S”).

10. The process of claim 1, wherein A is substituted with carboxylic acid groups and/or maleic anhydride groups.

11. The process of claim 1, wherein A is substituted with maleic anhydride groups.

12. The process of claim 1, wherein the material S-A-S is at least one of a polystyrene-poly(ethylene-butylene)-polystyrene (“SEBS”); and b polystyrene-poly(ethylene-butylene-styrene)-polystyrene (“S(EBS)S”).

13. The process of claim 1, wherein the material S-A-S is at least one of a polystyrene-poly(ethylene-butylene)-polystyrene (“SEBS”); and b polystyrene-poly(ethylene-butylene-styrene)-polystyrene (“S(EBS)S”); optionally substituted with carboxylic acid or maleic anhydride.

14. The process of claim 1, wherein the material S-A-S is at least one of a polystyrene-poly(ethylene-butylene)-polystyrene (“SEBS”); and b polystyrene-poly(ethylene-butylene-styrene)-polystyrene (“S (EBS)S”); substituted with maleic anhydride.

15. The process of claim 1, wherein the material S-A-S is at least one of: a. polystyrene-poly(ethylene-propylene)-polystyrene (“SEPS”); b. polystyrene-poly(ethylene-butylene)-polystyrene (“SEBS”); c. polystyrene-poly(ethylene-butylene-styrene)-polystyrene (“S (EBS) S”); and d. polystyrene-poly(ethylene-ethylene/propylene)-polystyrene (“SEEPS”).

16. The process of claim 1, wherein the cure initiating component is a photoinitiator component.

17. The process of claim 1, wherein A is substituted with carboxylic acid groups.

18. The process of claim 1, wherein, in a B stage cure product of the composition, the material S-A-S is present in an amount from about 5% to about 80% based on the total weight of the composition.

19. The process of claim 1, wherein, in a B stage cure product of the composition, the material S-A-S is present in an amount from about 30% to about 60% by weight based on the total weight of the composition.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings in which:

(2) FIG. 1 depicts an exploded view of various component layers of a hand held consumer electronic display device, about which overmolding may be used as the interface therebetween;

(3) FIG. 2 is a graph showing the bonding results achieved with Example 4 from Table 1; and

(4) FIG. 3 is a graph showing the bonding results achieved with Example 7 from Table 1.

DETAILED DESCRIPTION

(5) A polyolefin pin of diameter 12.65 to 12.675 mm and a minimum of 37.5 mm length is injection molded onto a metal or glass plate 101.6 mm×25.4 mm and thickness from 1.0 to 5.5 mm. The injection molding machine used was a Travin MINI MOULDER TP1, the barrel temperature used was 220° C., and the mold was unheated. The glass or metal plate has already been provided with a cured coating of the test formulation covering the surface. This coating is a B-staged version of the composition. It has been cured with a first cure mechanism, which is UV light, but can react when subsequently contacted with the melted thermoplastic, e.g. polyolefin. The coating thus has the material from the pin molded thereon.

(6) The test plastic used in the results below is polypropylene (sold under the trade name) TATREN IM 25 75, and the solid substrate used in the reported data is an anodised aluminium plate 101.6 mm×25.4 mm and thickness of 1.6 mm.

(7) This pin is pulled in a tensile test 24 hours after bonding at a rate of 2.0 mm/min using a Hounsfield tensile testing machine with a calibrated 5 kN load cell attached.

(8) Table 1 below is a list of additives that were tested in formulations specified in the Examples below. These compositions were applied to anodised aluminium and cured. Polypropylene was then injected moulded onto the cured films. The bond strengths measured at 24 hours post-bonding are included for each.

(9) TABLE-US-00001 TABLE 1 Bond Strength Example Achieved with PP to Product Polymer % S in Hardness Number Anodised Aluminium Manufacturer Name Material Polymer (shore A) 1 0.0 DuPont VCS5500 VAMAC (Ethylene 0 Acrylic Elastomer) 2 0.0 Nippon Auroren maleic anhydride 0 Paper 150S grafted PE 3 0.0 Mitsubishi Polytail H polyhydroxy 0 Chemicals Hydrogenated Polybutadiene 4 6.3 Kraton FG1901 maleic anhydride 30 71 grafted SEBS 5 3.0 Kraton FG1924 maleic anhydride 13 49 grafted SEBS 6 5.7 AKelastomers M1913 maleic anhydride 30 84 grafted SEBS 7 7.2 Kraton A1535 S(EBS)S 57 83 8 5.7 Kraton A1536 S(EBS)S 40 61 9 0.0 Kraton D1118 SB 33 64 10 0.0 Kraton D1116 SBS 23 63 11 0.0 Kraton D1155 SBS 31 87 12 8.1 AKelastomers H1517 SEBS 43 92 13 6.6 Kraton G1651 SEBS 31 70 14 5.7 AKelastomers H1041 SEBS 30 84 15 5.4 Kraton G1641 SEBS 33 58 16 5.1 Kuraray V9827 SEBS 30 78 17 5.0 Kuraray 8004 SEBS 31 80 18 4.7 AKelastomers H1051 SEBS 42 96 19 4.6 DzBh 502T SEBS 30 43 20 2.3 Kraton G1730 SEP 20 61 21 0.0 Kraton G1701 SEPS 37 64 22 0.0 Kraton D1170 SIBS 19 46 23 0.0 Kraton D1114 SIS 19 42

(10) In Table 1 the “% S in polymer” is the percentage of polystyrene by weight in the polymer.

(11) Example 1 (from Table 1) was the following formulation (the Polymer Material is the VAMAC material):

(12) TABLE-US-00002 Component % Xylene 20.00 MIBK 9.30 THFA 7.80 IBOA 4.00 VAMAC VCS5500 11.00 HEMA Phosphate 0.20 MA 1.50 BMI 0.10 BCHTU 0.80 TPO 0.70 Irgacure 184 0.40

(13) Examples 2 and 5 (from Table 1) were based on the following formulation. Only the Polymer Material differs between these Examples and the Example nos set out in Table 1 correspond to the following formulations with the Polymer Material being that indicated in Table 1 for the respective Examples.

(14) TABLE-US-00003 Component % MIBK 43.01 THFA 16.77 IBOA 8.60 Polymer Material 23.66 HEMA Phosphate 0.43 MA 3.23 BMI 0.22 BCHTU 1.72 TPO 1.51 Irgacure 184 0.86

(15) Example 3 (from Table 1) was the following formulation (the Polymer Material is the Polytail material):

(16) TABLE-US-00004 Component % MMA 51.61 2-HEMA 16.77 Polytail H 23.66 HEMA Phosphate 0.43 MA 3.23 BMI 0.22 BCHTU 1.72 TPO 1.51 Irgacure 184 0.86

(17) Examples 4 and 6 to 23 were based on the following formulation. Only the Polymer Material differs between these Examples and the Example nos set out in Table 1 correspond to the following formulations with the Polymer Material being that indicated in Table 1 for the respective Examples.

(18) TABLE-US-00005 Component % Xylene 33.06 MIBK 23.14 THFA 12.89 IBOA 6.61 Polymer Material 18.18 HEMA Phosphate 0.33 MA 2.48 BMI 0.17 BCHTU 1.32 TPO 1.16 Irgacure 184 0.66

(19) A graph showing further bonding results achieved with the composition of Example 4 on various combinations of substrates is shown in FIG. 2. The injection barrel temperature was 220° C.

(20) A graph showing further bonding results achieved with the composition of Example 7 on various combinations of substrates is shown in FIG. 3. The injection barrel temperature was 220° C.

(21) In the Examples above: THFA=Tetrahydrofurfuryl Acrylate; IBOA=Isobornyl Acrylate; FG1901 is a Maleic Anhydride Modified SEBS resin available from Kraton; Polytail H is a polyhydroxy hydrogenated polybutadiene HEMA Phosphate=Bis[2-(methacryloyloxy)ethyl] phosphate; MA=methacrylic acid; BMI=benzyl methyl imidazole; BCHTU=Benzoyl cyclohexyl thiourea; TPO=Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide-photoinitiator (as mentioned above) available from BASF; Irgacure 184 (as mentioned above) is a photoinitiator available from BASF chemical name 1-Hydroxy-cyclohexyl-phenyl-ketone); MIBK=methyl isobutyl ketone; and A1535 is a SEBS resin available from Kraton.

(22) Examples 1 to 3 are comparative examples. No bond strength is achieved.

(23) Examples 9, 10, 11, 22 and 23 are comparative examples. No bond strength is achieved. In this respect it is important to note that the “B” in the acronym for the materials is used in a non-unique manner, for example in SB; SIBS; and SBS the “B” stands for a polymer based on butadiene whereas in SEBS and S(EBS)S the “B” stands for a polymer based on butylene.

(24) The words “comprises/comprising” and the words “having/including” when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

(25) It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.