GB2101140A

GB2101140A - Internal mold release agent

Info

Publication number: GB2101140A
Application number: GB08218319A
Authority: GB
Inventors: Ramchandra Krishna Hulyalkar; Alvin Harold Lerner
Original assignee: Dart Industries Inc
Current assignee: Dart Industries Inc
Priority date: 1981-07-06
Filing date: 1982-06-24
Publication date: 1983-01-12
Also published as: JPS5815593A; FR2508919A1; SE8204157D0; BE893509A; DE3224206A1; SE8204157L; IL66161A0

Abstract

An internal mold release agent comprises a metal salt and an epoxidized vegetable oil and may be prepared by heating a metal salt such as zinc stearate with an epoxidized vegetable oil such as epoxidized soybean oil to obtain a homogeneous clear mixture. The mold release agent can be added directly to a polymeric molding composition and the polymeric system thus formed has the further advantage that it will gel at a significantly faster rate than an untreated system.

Description

SPECIFICATION Internal mold release agent Most polymeric molding systems, in particular those based upon polyurethanes or polyesters, suffer from the disadvantage that objects formed from such systems do not release quickly from the mold after their formation. This is due to the highly tenacious adhesivity of the polymer in the composition. A common practice to overcome this tenacious adherence to the mold in which the article is being formed is to coat a mold release agent on the surface of the mold. This of course requires the expenditure of both time and effort on the part of an operator. It must also be recognized that the use of a coated mold release agent results in the buildup of the agent on the surfaces of the mold to the extent that periodic cleaning of the mold is required, thus relating in the loss of time due to shutdown of the operation.In an effort to overcome this disadvantage, direct incorporation of a mold release agent such as zinc stearate into the polymeric system has been tried. However, such direct additions of internal mold release agents have not been successful in reaction injection molded polyurethane or polyester systems due to the difficulty of obtaining a uniform distribution of the zinc stearate in the polymer system.

It is therefore a constant objective of the art to provide an internal mold release agent which can be effectively employed in polyurethane and polyester systems.

Summary of the invention It has been found in accordance with the present invention that a successful and effective mold release agent can be provided by heating a metal salt of a long chain fatty acid with an epoxidized vegetable oil.

Such a mold release agent can be incorporated directly into the polyurethane or polyester system employed in reaction injection molding.

The mold release agent composition is readily prepared by heating a mixture of the metal salt and epoxidized vegetable oil to about 110 to 1 400C with continuing agitation. The preferred temperature range is from about 125"to about 135"C. The resulting clear homogeneous solution is cooled and added to the polymer system.

It has been found that the polymer system containing the mold release agent described above will release readily from the mold surfaces in marked contrast to a polymer system which does not contain a mold release agent.

As a further advantageous feature of the present invention it has also been found that the polymeric system containing the mold release agent of the present invention will gel at a significantly faster rate than the untreated system when the mold release agent is used as a third component along with the polyol and isocyanate in the preparation of a urethane. This demonstrates that the metal salt-epoxidized vegetable oil compositions of the present invention when so employed provide a catalyst effect in addition to imparting the desired mold release properties to the polymeric molding system.

While it is contemplated that the internal mold release agents provided by the present invention can be incorporated into any polymeric system, it has been found particularly advantageous when used in connection with a system based upon polyurethane or polyester resins. Such resins and molding systems based upon them are well known in the art.

The metal salt component of the mold release agent of the present invention can be any of the known metallic salts including calcium, barium, cadmium and other known metal salts of long chain fatty acid materials, including stearic, palmitic and oleic acids as well as the glycerides thereof. The metal salt component can be single salts or coformed salt systems consisting of two distinct metals such as are described, for example, in Example 5 set forth later in this specification. However, the use of zinc stearate as the metal salt component is particularly preferred.

The epoxidized vegetable oil can be any of the known vegetable oils, such as epoxidized soybean oil and epoxidized linseedate. However, the use of epoxidized octyl tallate is particularly preferred. In the general practice of the present invention the individual components will be present in the proportions of from about 20 to about 50 parts by weight of metal salt to about 80 to about 50 parts by weight of the epoxidized vegetable oil. The preferred range is from about 25 to about 40 of metal salt to about 75 to about 60 of epoxidized vegetable oil.

In preparing the mold release agent, the components can be dry mixed and then heated to a temperature and for a period of time sufficient to form a homogeneous solution. However, it is sometimes expedient to preheat the epoxidized vegetable oil prior to admixture with the metal salt component. A temperature of from about 1 10" to about 140can be employed over a time period of from about 15 to about 30 minutes.

The mold release agent is added to the polymeric system by direct admixture according to procedures well known in the art for the incorporation of additives into molding compositions.

The invention is illustrated in the examples given below. It is to be understood that the examples are illustrative only and not limitative of the present invention.

Example 1 10 parts of zinc stearate and 90 parts of epoxidized soybean oil are charged to a vessel, dry blended and then heated to 1 25" to 130"C with continuous stirring for about 15 minutes. A clear amber solution forms.

This solution is then cooled to room temperature, remaining a clear amber solution. This solution is added to a polyurethane reaction injection molded system, illustratively RIM 125 marketed by Union Carbide Corporation, in an amount sufficient to provide 1.5 percent by weight of zinc stearate in the system.

Example 2 35 parts of zinc stearate and 65 parts of epoxidized octyl tallate are charged to a vessel and heated to 125-1300C with continuous stirring for about 15 minutes. A clear amber solution forms. This solution is then cooled to room temperature, remaining a clear amber solution. This solution is added to a polyurethane reaction injection molding system in an amount sufficient to provide 1.5 percent by weight of zinc stearate in the system.

Example 3 30 parts of zinc stearate and 70 parts of octyl epoxy linseedate are charged to a vessel and heated to 125-130"C with continuous stirring for about 15 minutes. A clear amber solution forms which when cooled to room temperature remains a clear amber solution. This solution is added to a polyurethane reaction injection molding system in an amount sufficient to provide 1.8 percent by weight of zinc stearate in the system.

Example 4 45 parts of zinc stearate and 55 parts of Vikoflex 4050, an epoxy ester available from Viking Chemical Company, are charged to a vessel and heated to 125-130:C with continuous strirring for about 15 minutes. A clear light amber solution forms which, on cooling to room temperature remains a clear amber solution. This solution is added to a reaction injection molding system in an amount sufficient to provide 1.5 percent by weight of zinc stearate in the system.

Example 5 5 parts of magnesium stearate and 25 parts of zinc stearate were dry blended and added gradually in about 15 minutes to 70 parts of preheated octyl epoxytallate 1125-135-C) under continuous stirring. A clear amber solution forms. This solution is then cooled to room temperature and added to a polyurethane reaction injection molding system in an amount sufficient to provide 1.5 percent by weight of the mixed stearates.

Example 6 25 parts of zinc stearate and 75 parts of epoxidized soybean oil are charged to a vessel and heated to 125-130"C with continuous stirring for about 15 minutes. A clear amber solution forms. This solution is then cooled to room temperature at which point it remains a clear amber solution. This solution is added to a polyurethane reaction injection molding system in an amount sufficient to provide 1.8 percent by weight of zinc stearate in the system.

After molding, the article formed from the reaction injection molding compositions containing the mold release agents of Examples 1-6 releases readily from an aluminum dish. Systems employing the same polyurethane reaction injection molding compositions but not containing the mold release agents of Examples 1-6 adhere tenaciously to the dish on molding.

The following Example illustrates this.

Example 7 An internal mold release agent was prepared according to the procedure of Example 2 and was incorporated into a urethane reaction injection molding composition "RIM 125" in an amount by weight of 5 parts per 100 parts of total composition, and the resulting composition was cured on an aluminum substrate at 160"flora period of one minute.

A comparison specimen consisting of RIM 125 was similarly cured at 160"F for a period of one minute.

The peel force required to release the specimens from the aluminum substrate was measured with the following results: Peel force Specimen in pounds linear inch a) RIM 125 32.4 b) RIM 125 + 5 pph of product of Example 5 12.5 The above tests were repeated employing a chrome plated steel substrate in place of the aluminum substrate.

The following results were observed: Peel force Specimen in poundsllinear inch a) RIM 125 25.7 b) RIM 125 + 5 pph of 8.0 product of Example 5 The markedly superior release properties imparted by the use of the mold release agents of the present invention are readily apparent from the results of the foregoing tests.

Claims

1. An internal mold release composition comprising 5 to 50 parts by weight of a metal salt and 95 to 50 parts by weight of an epoxidized vegetable oil.

2. A composition according to claim 1 wherein the metal salt is zinc stearate.

3. A composition according to claim 1 or 2 wherein the epoxidized vegetable oil is expoxidized soybean oil.

4. A composition according to claim 1 or 2 wherein the epoxidized vegetable oil is octyl epoxy tallate.

5. A composition according to any one of claims 1 to 4 wherein the proportion of metal salt to epoxidized vegetable oil is from 1 to 10 to 1 to 1.

6. A composition according to claim 1 substantially as described with reference to any one of Examples 1 to6.

7. Use of a composition as claimed in any one of the preceding claims as an internal mold release agent in a polymeric molding system.

8. A process for the reaction injection molding of a polymeric system based upon polyurethane or polyester, which comprises incorporating into the polymer system an internal mold release agent comprising 0.5 to 5 parts by weight of metal salt and 1.5 to 15 parts by weight of epoxidized vegetable oil.

9. A process according to claim 8 wherein the metal salt is zinc stearate.

10. A process according to claim 8 or 9 wherein the epoxidized vegetable oil is epoxidized soybean oil.

11. A process according to claim 8 or 9 wherein the epoxidized vegetable oil is octyl epoxy tallate.

12. A process according to any one of claims 8 to 11 wherein the proportion of metal salt to epoxidized vegetable oil is from 1 to lotto 1 to 1.