HK1090603B - Mold release composition and process therewith - Google Patents

Description

Mold release composition and method of using same

Technical Field

The invention relates to a composition which can be used as a mold release agent and to a method for applying a thin continuous film of mold release agent to a mold.

Background

In commercial practice, the release agent, which is typically a polymer or a combination of polymers, may be an emulsion or dispersion in a solvent. If dispersed in a solvent, the solvent is used as a medium to wet the surface of the sizing mold and the release agent is applied to the mold. However, silicone resins, which are commonly used as release agents, often do not coat surfaces well when dispersed in typical hydrocarbon solvents. The silicone resin lumps on the coated surface, so a continuous film could not be obtained.

There is therefore an increasing need to develop new mould release agents which are capable of forming a thin continuous coating film on the mould surface.

Summary of The Invention

The present patent provides a composition comprising a solvent; silicone resins, rubbers or fluids; and optionally, a catalyst, a co-solvent, or both, wherein the solvent is a volatile siloxane.

The present invention also provides a method of applying a thin continuous coating film to a mold, the method comprising the steps of: combining together a solvent, a silicone resin or silicone rubber or silicone fluid, and, optionally, a catalyst, a co-solvent, or both, to form a mold release composition; applying the release agent composition onto or onto a mold, and optionally curing the composition, wherein the solvent is a volatile siloxane.

Detailed Description

According to the present invention, the term "mold" refers to one or more forming surfaces. Any volatile silicone may be used as a solvent for the compositions of the present invention. The term "volatile siloxane" refers to a siloxane that evaporates rapidly at the temperature and pressure of use. Generally, the volatilization rate is greater than 0.01 for n-butyl acetate, assuming a volatilization rate of 1 for n-butyl acetate.

Suitable solvents may be of the formula R (R)₂SiO)_xSiR₃Or (R)₂SiO)_yWherein each R may be the same or different and is preferably an alkyl, alkoxy, phenyl, phenoxy, or a combination of two or more thereof; each group contains from 1 to about 10, preferably from 1 to about 8 carbon atoms. R may also be a halogen atom. Most preferably, R is a methyl group and may be substituted with a halogen, amine or other functional group. The subscript x may be a number of from 1 to about 20, preferably from 1 to 10. The subscript y may be a number of from 3 to about 20, preferably from 3 to about 10. Preferably, the solvent has a molecular weight in the range of about 50 to about 1,000 and a boiling point of less than about 300 deg.C, preferably less than 250 deg.C, more preferably less than 200 deg.C and most preferably less than 150 deg.C.

Examples of suitable methyl siloxanes include, but are not limited to, hexamethyldisiloxane, hexamethylcyclotrisiloxane, 2, 5-dichloro-1, 1, 3, 3, 5, 5, -hexamethyltrisiloxane, 1, 3-dimethyltetramethoxydisiloxane, 1, 1, 1, 3, 5, 5, 5-heptamethyltrisiloxane, 3- (heptafluoropropyl) trimethylsiloxane, octamethyltrisiloxane, octamethyltetrasiloxane, octamethylcyclotetrasiloxane, decamethyltetrasiloxane, decamethylcyclopentasiloxane, dodecamethylpentasiloxane, and dodecamethylcyclohexasiloxane, and combinations of two or more thereof.

Any silicone resin, rubber or fluid compatible with the volatile silicones disclosed above may be used. Typically a polyorganosiloxane. For example, methoxy-terminated polyalkylsiloxanes and hydroxy-terminated polydimethylsiloxanes can be used. A suitable silicone resin, rubber and fluid may be one of a resin, rubber or fluid. Examples of suitable polyorganosiloxanes include polydimethylsiloxane, polymethylhydrosiloxane, polysilsesquioxane, polytrimethylsiloxane, polydimethylsiloxane, and combinations of two or more thereof. Each silicone resin may also contain functional groups such as halide groups, amine groups, hydroxyl groups, epoxy groups, carbinol groups, carboxylate groups, acetoxy groups, alkoxy groups, acrylate groups, and combinations of two or more thereof. The molecular weight may be from about 500 to about 1,000,000. One preferred silicone resin is a silicon-bonded hydroxyl terminated polyorganosiloxane, which is well known and commercially available.

The silicones and silicone resins, rubbers or fluids disclosed above are generally commercially available, for example, from Dow Corning Chemicals, Midland, Michigan and general electric company, Fairfield, connection.

Any organic solvent, preferably substantially anhydrous, such as a hydrocarbon or halogenated hydrocarbon, which is inert to the other components of the composition, compatible with the volatile silicone, and rapidly volatile when applied to the mold surface can be used as a co-solvent. The co-solvent also reduces the viscosity of the composition and facilitates polymer release. Preferably, the normal boiling point of the co-solvent is less than about 300 deg.C, preferably less than 200 deg.C, and most preferably less than 150 deg.C, depending on the temperature of the release agent composition to be applied to the mold. The lower the temperature at which the release agent composition is to be applied, the lower the boiling point of the solvent is preferred, and vice versa. Examples of suitable co-solvents include, but are not limited to, octane, decane, cyclohexane, toluene, xylene, methyl chloride, methylene chloride, 1, 2-dichloroethane, carbon tetrachloride, chloroform, perchloroethylene, acetone, methyl ethyl ketone, ethyl acetate, tetrahydrofuran, dioxane, white spirit, mineral spirits, naphtha, and combinations of two or more thereof.

The mold release composition may also contain other silicon compounds such as modified fumed silica, surfactants, fluoropolymers such as polytetrafluoroethylene, waxes, fatty acids such as stearic acid, fatty acid salts such as metal stearates, finely divided solids such as talc, emulsifiers, biocides, corrosion inhibitors, and the like.

Each of the components disclosed above may be present in the composition in an effective amount sufficient to allow proper release of the molded article. For example, the solvent may be present in the composition in an amount of about 10 to about 99% and the silicone resin may be present in the composition in an amount of about 0.1 to about 90%, based on the total weight of the composition. The co-solvent, if used, may be present in the composition in an amount such that the sum of the solvent and the co-solvent is from about 10 to about 99%, provided that the solvent is present in an amount of at least about 10%, preferably at least 20%. Other components, if present, may range from about 0.01 to about 10%.

Any catalyst that can catalyze or enhance the cure of a composition comprising a volatile siloxane, a siloxane resin, and a solvent can be used herein. Preferred catalysts are organic titanium compounds. Tetrahydrocarbyltitanium oxides, also called tetraalkyl titanates, are highly preferred organotitanium compounds because they are readily available and effective. Examples of suitable titanium compounds include those of the formula Ti (OR)₄Wherein each R is independently selected from the group consisting of alkyl, cycloalkyl, alkaryl, and hydrocarbyl radicals, each radical containing from 1 to about 30 carbon atoms, preferably from 2 to about 18, and very preferably from 2 to about12 carbon atoms and each R may be the same or different. Tetrahydrocarbyltitanium oxides containing from 2 to about 12 carbon atoms per hydrocarbyl group and all being linear or branched alkyl groups are highly preferred because they are less expensive, more readily available and effective for curing the composition. Suitable titanium compounds include, but are not limited to, titanium tetraethoxide, titanium tetrapropoxide, titanium tetraisopropoxide, titanium tetra-n-butoxide, titanium tetrahexoxide, titanium tetra-2-ethylhexoxide, titanium tetraoctoxide, and combinations of two or more thereof.

Other catalysts suitable for use include compounds containing elements from group VIII of the periodic Table of the elements, such as platinum, palladium, iron, zinc, rhodium and nickel, and tin or zirconium compounds. Examples of other suitable catalysts include, but are not limited to, dibutyltin diacetate, dibutyltin dilaurate, zinc acetate, zinc octoate, zirconium octoate, and combinations of two or more thereof. For example, dibutyltin diacetate can be used alone or in combination with a titanium compound.

These catalysts are believed to be commercially available. For example, TYZOR, marketed by Delaware DuPont, Wilmington, USA^®TPT and TYZOR^®TBT (tetraisopropyl titanate and tetra-n-butyl titanate, respectively).

The various catalysts disclosed above may be used in the composition in an amount of about 0.01 to about 10 weight percent of the silicon polymer.

The compositions may be produced by any method known to those skilled in the art, for example, by mixing the components disclosed above. Preferably, the catalyst is introduced after the silicone resin, solvent, and optional co-solvent are combined.

The method for coating a thin continuous coating film on a mold comprises the following steps: (1) combining a solvent, a silicone resin or silicone rubber or silicone fluid, and optionally a co-solvent, a catalyst, or both, to form a mold release composition, (2) applying or coating the mold release composition onto a mold, and optionally, (3) curing the mold release composition. The mold release composition may be the same as the compositions disclosed above. Application of the mold release composition can be carried out by any method known to those skilled in the art, such as spraying, brushing, wiping, dipping, and combinations of two or more thereof. Any surface of the forming mold may be coated with the release agent composition. Curing may be carried out by any method known to those skilled in the art, for example, curing at ambient temperature, such as from about 25 ℃ to about 200 ℃, and at a pressure compatible with the temperature range, such as atmospheric pressure, for from about 1 second to about 2 hours. Generally, curing is carried out at the temperature and pressure at which molding is carried out.

To produce the molded article, the molding material or material to be molded may be introduced or introduced into the mold by any method known to those skilled in the art, such as pumping, extrusion, blending, or other suitable methods known to those skilled in the art. The molded article is then produced and may be removed or demolded by any method known to those skilled in the art. Since methods of making molded articles are well known in the art, they will not be described in detail herein for the sake of brevity.

The molding material may be any material that can be molded, including, but not limited to, plastics, polymers, glass, ceramics, and metals. Examples of the polymer include thermosetting resins or thermoplastic resins. Specific examples include acrylonitrile-butadiene-styrene, acrylonitrile-chlorinated polyethylene-styrene, acrylic acid-styrene-acrylonitrile, polyacetal homopolymers and copolymers, acrylic acid, cellulose, fluorinated polymers, polyamides, polyacrylates, polybutenes, polycarbonates, polyesters, polyethylene, ethylene-acid copolymers, ethylene-ethyl acrylate, ethylene-methyl acrylate, polymethyl methacrylate, polybutyl methacrylate, ethylene-vinyl acetate, ethylene-vinyl alcohol copolymers, ionomers, polymethylpentene, polyphenylene oxide, polypropylene, ethylene-propylene copolymers, polypropylene impact copolymers, polypropylene random copolymers, polystyrene, styrene-acrylonitrile, styrene-butadiene copolymers, polypropylene, polyethylene-styrene copolymers, polyethylene-styrene, Styrene-ethylene-butylene-styrene, styrene-maleic anhydride copolymers, polyvinyl chloride, vinylidene chloride homopolymers and copolymers, styrene block copolymers, polyolefin blends, elastomeric alloys, thermoplastic polyurethanes, polyethylene terephthalate, polybutylene terephthalate, thermoplastic copolyesters, polyethers, thermoplastic polyamides, polyether-polyamide block copolymers, allyl molding compounds, bismaleimides, epoxy resins, phenolic resins, polyesters, ethylene-propylene-diene terpolymers such as EPDM rubber, polyimides, ionomers, polyurethanes, multi-block polyurethanes, reaction injection molded polyurethanes, polysiloxanes, urea-melamine formaldehyde resins, polyacetals, polyesters, polyamides, ionomers, and combinations of two or more thereof. These polymers are well known to those skilled in the art.

Examples

The following examples are illustrative of the present invention and should not be construed as unduly limiting the scope of the invention.

Example 1 this example illustrates that thinner continuous silicone resin coatings can be obtained with volatile methyl siloxanes than with petroleum ether.

A mold release composition comprising the following components was spray coated onto a 1 inch x 3 inch (2.54cm x 7.62cm) microscope slide that had been previously weighed and heated to 65 ℃ in the amounts indicated in the following table: 80% solvent (petroleum ether or octamethylcyclotetrasiloxane (volatile methyl)), 20% siloxane resin and fluid, and about 0.2% catalyst (based on the total weight of the solvent, resin, and fluid; TYZOR)^®TBT and dibutyltin diacetate). After allowing the solvent to evaporate in a fume hood for a sufficient time, the release agent was cured at 65 ℃ for 2 minutes. The slides were then reweighed and visually inspected under a microscope to estimate the silicone resin coverage of the slide surface. The results are shown in Table 1.

TABLE 1

Coating amount (mg)	Petroleum ether	Methylsiloxane
			0.7		100% coverage
0.9	20% coverage
			1.9	40％
2.8	65％	100％
			3.1	70％
3.5		100％
			8.4	95％
19.4	98％
			38.2	100％

On slides coated with petroleum ether as solvent, the coating was very irregular and pimple-button. The coating with methylsiloxane as solvent was very smooth. Replacing petroleum ether with mineral spirits further accentuated the pimples of silicone resin on the slides.

Example 2 this example serves to illustrate how various methyl siloxane solvents can be used to promote the formation of smooth continuous coatings from various siloxane resins, fluids and functional fluids applied at high temperatures.

The silicone resin, fluid and functional fluid were dispersed in various hydrocarbon solvents and volatile methyl siloxanes at a concentration of 5 wt% polymer solids and 95 wt% solvent. The silicon polymer and solvent were sprayed onto a 1 inch x 3 inch (2.54cm x 7.62cm) microscope slide pre-weighed and heated to 65 ℃ using a Preval sprayer. After the solvent had evaporated, the slides were reweighed to determine the coating weight and the coating was visually inspected for smoothness and coverage as shown in table 2.

TABLE 2

		Coating layer					Coating layer
										SP1	Solvent(s)2	Weight (mg)	Morphology of	Coverage rate	SP1	Solvent(s)2	Weight (mg)	Morphology of	Coverage rate
A	Toluene	1.8	Spots of spots	Incomplete	A	OMS	0.8	Is smooth and smooth	Complete (complete)
										B	PE	2.7	Roughness of	Incomplete	B	DMS	4.1	Is smooth and smooth	Complete (complete)
B	MS	1.6	Lump with pimples	Incomplete	B	---
										B	Acetone (II)	3.0	Roughness of	Incomplete	B	---
C	MS	3.3	Lump with pimples	Incomplete	C	OMS	2.6	Is smooth and smooth	Complete (complete)
										C					C	DMS	3.2	Is smooth and smooth	Complete (complete)
D	S	1.2	Lump with pimples	Incomplete	D	OMS	1.7	Is smooth and smooth	Complete (complete)
										D					D	OMTS	3.5	Is smooth and smooth	Complete (complete)

¹SP represents a siloxane polymer; polymer a is a hydroxyl-terminated methylsilsesquioxane-dimethylsiloxane copolymer; polymer B is a methoxy-terminated methylsilsesquioxane-dimethylsiloxane copolymer; polymer C was 14,000CSt (centistokes) hydroxy terminated polydimethylsiloxane; and polymer D is 60,000CSt (centistokes) polydimethylsiloxane.

²PE is petroleum ether; MS is mineral spirit; s is Stoddard solvent; OMS represents octamethylcyclotetrasiloxane; DMS is decamethyltetraA siloxane; and OMTS is octamethyltrisiloxane.

The results show that the silicon polymer dispersed in the OMS formed a smooth continuous film, while the same polymer dispersed in the hydrocarbon solvent produced a rough and incomplete film.

Example 3 this example illustrates how a volatile methyl siloxane solvent can be used to promote the formation of a smooth continuous coating of room temperature coated silicone polymer.

One sample of silicone rubber was dispersed in petroleum ether while a second sample of the same silicone rubber was dispersed in an OMS fluid at a concentration of 5 wt% polymer solids and 95 wt% solvent. The silicone polymer and solvent were sprayed onto a pre-weighed 1 inch x 3 inch (2.54cm x 7.62cm) room temperature microscope slide using a Preval sprayer. After the solvent had evaporated, the slides were reweighed to determine the coating weight and the coating was visually inspected for smoothness and coverage as shown in table 3.

TABLE 3

		Coating layer					Coating layer
										SP1	Solvent(s)2	Weight (m)g)	Morphology of	Coverage rate	SP1	Solvent(s)2	Weight (mg)	Morphology of	Coverage rate
D	PE	4.1	Roughness of	Incomplete	D	75/25 wt% OMS/OMTS	2.5	Is smooth and smooth	Complete (complete)

¹SP represents a silicon polymer; polymer D was 60,000CSt (centistokes) polydimethylsiloxane.

²PE is petroleum ether; OMS represents hexamethyldisiloxane; OMTS is octamethyltrisiloxane.

The results show that the silicon polymer dispersed in the OMS formed a smooth continuous film when coated at room temperature, while the same polymer dispersed in the hydrocarbon solvent produced a rough and incomplete film.

Example 4 this example serves to illustrate how volatile methyl siloxane can be used to facilitate the formation of a smooth thin coating with a standard formulated silicon release agent.

A commercial mold release agent for plastic, adhesive and elastomer products is commercially available. The manufacturer's description of the product is as follows: contains 50% active material comprising trimethylated silica and tetrakis (trimethylsiloxy) silane, and uses a hydrocarbon solvent mixture consisting of Stoddard solvent, xylene, and ethylbenzene. Manufacturer specifications recommend diluting 10 parts of the release agent with 80 parts isopropanol and 10 parts toluene to improve surface wetting. The release agent was diluted with 10/80/10 wt% of a mixture of release agent, isopropanol and toluene to a polymer solids content of 5 wt% following the manufacturer's recommendations. The mold release coating was then sprayed onto a 1 inch by 3 inch (2.54cm by 7.62cm) microscope slide that was previously weighed and heated to 65 ℃ using a Preval sprayer. After the solvent evaporated, the slides were reweighed to determine the coating weight and visually inspected for coating smoothness and coverage. For comparison, the release agent was diluted in Octamethyltrisiloxane (OMTS) and the polymer solids content was still 5 wt% and coated on a glass slide using the method described. The results show that the manufacturer's recommended hydrocarbon solvents produce an incomplete coating of specks, while the use of OMS solvents produces a smooth continuous coating. The results are shown in Table 4, where IPA is isopropanol.

TABLE 4

	Coating layer				Coating layer
								Solvent(s)	Weight (mg)	Morphology of	Coverage rate	Solvent(s)	Weight (mg)	Morphology of	Coverage rate
80/10 IPA/toluene	3.0	Roughness of	Incomplete	OMTS	3.3	Is smooth and smooth	Complete (complete)

Example 5 this example serves to illustrate how the formation of a smooth continuous coating improves the performance of the release agent.

Release agents using methylsilsesquioxane-dimethylsiloxane copolymer and polydimethylsiloxane fluids were dispersed in a variety of solvents to a solids concentration of 5 wt.%. The coating was sprayed onto a 9 inch x 12 inch x 3 inch (22.86cm x 30.48cm x 7.62cm) aluminum box mold that was pre-weighed and heated to 65 ℃ using a Preval sprayer. After the solvent had evaporated, the mold was allowed to cool to room temperature and reweighed. The mold was then heated again and filled with a flexible toluene diisocyanate-based polyurethane foam resin. The mold lid was closed and the expanded foam was allowed to cure for 6 minutes in an oven thermostatted at 65 ℃. The foam was then removed from the mold by hand. If the foam can be successfully removed from the mold without tearing, the mold is filled with the polyurethane resin without further application of the release agent. This was repeated until foam tear was observed. The results are shown in Table 5, wherein the abbreviations are as in Table 1.

TABLE 5

Solvent(s)1	Cured coating weight	Number of demolds before foam tearing
			OMS	0.12g	14
50/50 wt% hybrid OMTS/DMS	0.12g	10
			10/20/10/60 wt% blend 244/1.0/1.5/75OMS/OMTS/DMS/MS	0.14g	12
Solvent oil	0.13g	1

¹Abbreviations see the preceding tables

The results show that release agent coatings dispersed in OMS fluid or OMS in combination with hydrocarbon solvents provide a significant improvement in performance over hydrocarbon solvents alone.

Claims (10)

1. A method comprising combining a solvent and a silicone resin to form a mold release composition, the silicone resin being a polysilsesquioxane; and applying the composition to or onto a mold, wherein the solvent has the formula R (R)₂SiO)_xSiR₃Or (R)₂SiO)_yWherein each R is a methyl group or a methyl group substituted with a functional group, x is 1 to 20, and y is 3 to 20.

2. The method according to claim 1, further comprising curing the composition.

3. The method according to claim 1, wherein the composition further comprises a catalyst, a co-solvent, or both.

4. The method according to claim 1, 2 or 3, wherein the solvent is hexamethyldisiloxane, hexamethylcyclotrisiloxane, 2, 5-dichloro-1, 1, 3, 3, 5, 5-hexamethyltrisiloxane, 1, 3-dimethyltetramethoxydisiloxane, 1, 1, 1, 3, 5, 5, 5-heptamethyltrisiloxane, 3- (heptafluoropropyl) trimethylsiloxane, octamethyltrisiloxane, octamethylcyclotetrasiloxane, decamethyltetrasiloxane, decamethylcyclopentasiloxane, dodecamethylpentasiloxane, dodecamethylcyclohexasiloxane, or a combination of two or more thereof.

5. The method according to claim 4, wherein the solvent is octamethyltrisiloxane, octamethylcyclotetrasiloxane, decamethyltetrasiloxane, or a combination of two or more thereof.

6. The process according to claim 3, wherein the composition comprises the catalyst, and wherein the catalyst is a titanium compound, dibutyltin diacetate, or a combination thereof.

7. The method according to claim 1, further comprising modified fumed silica, a surfactant, a fluorinated polymer, a wax, a fatty acid salt, a finely divided solid, an emulsifier, a biocide, a corrosion inhibitor, or a combination of two or more thereof.

8. A method according to any one of claims 1 to 3, further comprising introducing a moulding material into or onto said mould, converting said material into a moulded article, and recovering said article.

9. The method of claim 4, further comprising introducing a molding material into or onto said mold, converting said material into a molded article, and recovering said article.

10. A molding die having coated on its surface a release agent composition comprising a solvent and a silicone resin, said silicone resin being a polysilsesquioxane, wherein said solvent has the formula R (R)₂SiO)_xSiR₃Or (R)₂SiO)_yWherein each R is methyl or methyl substituted with a functional group, x is 1 to 20, and y is 3 to 20.