Plastic material for industrial former

Abstract

The present invention relates to a plastic material for use in various application. Further, the present invention relates to a plastic material for an industrial former (herein also designated as a mold). Additionally, the present invention relates to a mold made of a plastic material and the method for the manufacture of said mold. Furthermore, the present invention relates to an industrial process using such mold, such as in a process for making rubber goods comprising dipping of a mold into a rubber emulsion, wherein the mold consisting of a plastic material having a surface tension in the range from 25 to 60 mJ/m2 measured according to ASTM standard D-2578/09.

Claims

1. A process for manufacturing a mold-formed rubber product comprising the steps of: (i) providing a mold which is formed of a plastic material having a surface tension in the range from 25 to 60 mJ/m.sup.2 measured according to ASTM standard D-2578/09, wherein the plastic material is a thermoplastic material comprising a semi-crystalline semi-aromatic polyamide or copolymers thereof, or a blend comprising a semi-crystalline semi-aromatic polyamide, an aliphatic polyamide or copolymers thereof, or a blend comprising an aliphatic polyamide; (ii) roughening a surface of the mold to achieve a surface roughness (Ra) of between 4 and 6 μm; (iii) cleaning the mold surface with one or more water-based solutions including one or more rinsing steps; (iv) brushing the mold surface; (v) applying onto the mold surface a coagulant solution containing salt dissolved in water, a mold release agent and a wetting agent following by drying to thereby form a surface pretreated mold; (vi) drying the mold; and thereafter (vii) dipping the dried mold into a rubber emulsion to thereby provide on the mold the mold-formed rubber product.

2. The process according to claim 1, wherein the plastic material comprises a reinforcement filler.

3. The process according to claim 1, wherein the surface tension is in the range from 35 to 50 mJ/m.sup.2 measured according to ASTM standard D-2578/09.

4. The process according to claim 1, wherein the plastic material is a thermoplastic material comprising a polyamide or a copolymer thereof, or a blend comprising a polyamide having a melting temperature or a glass transition temperature equal to or above 150° C. measured by DSC at a heating rate of 10° C./min in the second heating cycle according to standard ISO 11357-3 (2009).

5. The process according to claim 1, wherein the surface roughening step (ii) comprises sandblasting the mold surface.

6. The process according to claim 5, wherein the sandblasting comprises directing glass beads with a diameter of from 0.2-0.8 mm toward the surface of the mold.

7. The process according to claim 1, wherein the mold release agent of the coagulant solution comprises a stearate-based component.

8. The process according to claim 1, which further comprises the step of rinsing the mold at least once with water at or above ambient temperature.

9. The process according to claim 1, which further comprises the steps of: (viii) curing the rubber product on the mold; and thereafter (ix) removing the rubber product when cured from the mold.

Description

EXAMPLES

(1) E1 to E10 are Examples according to the present invention.

(2) CE1 to CE5 are Comparative Examples

(3) Molds Made of Different Materials

(4) TABLE-US-00002 TABLE 1 quality of rubber good manufactured with molds made of different materials CE1 CE2 E1 E2 E3 E4 E5 Material M1 M2 M3 M4 M5 M6 M7 Surface Nm 31 42 42 42 38 51 tension of the polymer compound (mJ/m.sup.2) Quality of good bad, good good good good good rubber good thinning before and ageing pinholes Surface pitted/ good, good, good, good, good, cracked quality of the chipped intact intact intact intact intact surface mold after surface base wash resistance test Quality of Bad, bad, good good good good medium, rubber good pinholes thinning some after base and pinholes wash pinholes resistance test Surface good, good, good, good, good, good, cracked quality of the intact intact intact intact intact intact surface mold after acid wash resistance test Quality of good bad, good good good good medium, rubber good thinning some after acid and pinholes wash pinholes resistance test Drop test bad, good good good good good good broken Legend: Nm—Not measured

(5) MuCell Injection Molding Process

(6) Two materials were tested: M5 and M8 (as described above).

(7) Both materials were molded using standard injection molding (S) and using MuCell technology/molding (M). The MuCell technology was carried out in order to obtain a determined weight reduction: respectively 5 wt. %, 10 wt. %, 25 wt. %, 30 wt. % as indicated in the table below.

(8) Materials M5 and M8 allowed molding thick parts by MuCell technology thereby obtaining an article without sink marks when using a small amount of injected gas, while for standard injection molded plaques, sink marks appear on the manufactured mold which also appear on the rubber good fabricated thereof.

(9) The materials with an semi-crystalline polyamide and an amorphous polyamide are thus advantageously processed using MuCell technology: they can be processed while allowing a higher weight reduction and provide a better appearance article/mold than when the materials do only comprise a semi-crystalline polyamide (no amorphous polyamide).

(10) When blending the sc-PPA with am-PPA, the weight reduction using MuCell molding without surface defects on the plaque is much higher when compared to using PPA. The rubber good resulting from the MuCell molded former according to E7, E8 and E9 are of good quality, thus better quality than by standard injection molding or when the Mucell molding is carried out with a material which does not comprise both sc-PPA and am-PPA.

(11) Both standard and MuCell molding were performed on 75×50×20 mm plaque molds. The weight reduction was controlled by adjusting the amount of N2 injected into the melt. The dipping procedure of the plastic compositions was performed on sandblasted injection molded plaques with an arithmetical mean surface roughness Ra of 4-6 μm.

(12) TABLE-US-00003 TABLE 2 quality of rubber good manufactured with molds made of different plastic materials and the maximum weight reduction when using MuCell molding without surface defects on the plaque. CE5 CE6 CE7 E6 E7 E8 E9 E10 Material M8 M8 M8 M5 M5 M5 M5 M5 Standard (S) or S M M S M M M M MuCell (M) Molding Weight reduction 0 5 10 0 5 10 25 30 when performing MuCell molding (wt %) Appearance sink marks Good bad, gas Sink marks good good good bad, gas molded plaque breaking breaking through the through the surface surface Quality of sink mark good bad, large Sink mark good good good bad, large rubber good visible pinholes visible pinholes