KR20020030080A - Coating of Liquid Crystalline Polymers with Fluoropolymers - Google Patents

Abstract

The liquid crystal polymer part may be coated with a fluoropolymer. Parts coated with fluoropolymers are useful for chemical process equipment and oven containers.

Description

Coating of Liquid Crystal Polymers with Fluoropolymers {Coating of Liquid Crystalline Polymers with Fluoropolymers}

Thermotropic (melt processability) liquid crystal polymers (LCPs) are known to have various good properties including good melt processability, high temperature resistance, good chemical resistance and good flame retardancy. Due to these and other properties, the liquid crystal polymers are particularly useful for oven vessels and other applications where some or all of these properties are valuable. However, like many other materials used in cooking and other applications, food or other materials will contaminate and / or stick to the LCP surface. As is known to those who cook, it is common to coat the surfaces which come into contact with the food, especially during cooking and / or heating, with a material such as a fluoropolymer to which the food does not stick.

Since fluoropolymers do not adhere well to other materials, it is often necessary to treat the substrate surface to improve the adhesion of the fluoropolymer layer, which can often be done by surface treating the substrate and / or using primers. Such treatment may appear to be much more difficult to those skilled in the LCP field because LCP is known to be relatively chemically stable and poorly adhered to other materials. We have coated LCP with a fluoropolymer so that LCP is not completely coated (encapsulated) and / or does not contain a large surface area and is coated on only one or more surfaces, even in oven containers and other applications. It has been found that good adhesion can be obtained to a degree sufficient for use.

Japanese Patent Application No. 3-95954 describes coating an LCP wafer carrier with a fluoropolymer. However, there is no mention of surface treatment of LCPs prior to coating or coating of only a single surface.

Summary of the Invention

The present invention relates to a part made of a thermotropic liquid crystal polymer and coated with a fluoropolymer coating. Preferably this part is an oven vessel part.

Oven containers made of liquid crystal polymers (LCPs) can be coated with fluoropolymers to obtain LCP oven container parts with a so-called non-stick surface.

Several terms are used herein and are defined as follows.

"Fluoropolymer" is a synthetic polymer containing fluorine directly bonded to carbon. Preferably, the fluoropolymer contains at least about 25 wt% fluorine, more preferably at least about 40 wt% fluorine, particularly preferably at least about 50 wt% fluorine. One type of preferred fluoropolymer is a perfluoro fluoropolymer.

-(Thermotropic) "Liquid Crystal Polymers" are polymers that are anisotropic when tested by the "TOT" test as described in US Pat. No. 4,118,372. Preferred LCPs are polyesters and poly (ester-amides), with polyester being more preferred.

Any thermotropic LCP can be used in the method. Suitable thermotropic LCPs are described in, for example, US Pat. Nos. 3,991,013, 3,991,014, 4,011,199, 4,048,148, 4,075,262, 4,083,829, 4,118,372, 4,122,070, 4,130,779, 4,153, 4,159,365, 4,161,470, 4,169,933, 4,184,996, 4,189,549, 4,219,461, 4,232,143, 4,232,144, 4,245,082, 4,256,624, 4,269,965, 4,269,965 4,370,466, 4,383,105, 4,447,592, 4,522,974, 4,617,369, 4,664,972, 4,684,712, 4,727,129, 4,727,131, 4,728,714, 4,749,769,927,4,762,907 4,816,555, 4,849,499, 4,851,496, 4,851,497, 4,857,626, 4,864,013, 4,868,278, 4,882,410, 4,923,947, 4,999,416, 5,559,721,722 5,025,082, 5,086,158, 5,102,935, 5,110,896 and 5,143,956, and European Patent Application No. 356,226. Things. Useful thermotropic LCPs include polyesters, poly (ester-amides), poly (ester-imides), and polyazomethines. Preferred thermotropic LCPs are polyesters or poly (ester-amides), with particular preference being given to the polyesters or poly (ester-amides) being partially or fully aromatic. Aromatic means that the aromatic group forms the main chain (skeleton) of the LCP, and any functional group (ether, ester, amide, etc.) is connected to the aromatic group, and the aliphatic group is bound to the aromatic group, such as a repeating unit derived from t-butylhydroquinone. It may be.

In many instances, the LCP used has a relatively high melting point, preferably greater than about 300 ° C. when the melting endothermic peak is taken as the melting point in the second heating cycle as measured by a differential scanning calorimeter at a heating rate of 10 ° C./min, More preferably greater than about 325 ° C, even more preferably greater than about 350 ° C, even more preferably greater than about 400 ° C.

The fluoropolymer can be applied in any way. For example, it may be a film laminated by applying heat and pressure to the surface of the LCP. A particulate material, preferably a powder or powder suspended in a liquid such as water (such as an emulsion or dispersion), which is sprayed onto the surface of the LCP to be coated (in the case of powder, electrostatic sprayed) or by a doctor knife, or otherwise It can apply | coat by a coating method. The liquid carrier, if present, is usually removed by volatilization and then baked until the coating forms a binder film that preferably adheres to the substrate, in this case a treated LCP surface. In the case of fluoropolymers having a relatively high fluorine content, this baking is often done at substantial high temperatures above 300 ° C. for a substantial time, such as 10 to 60 minutes. Thus, when such coatings are used, it is desirable that the melting point of the LCP is relatively high so that the shape and / or dimensions of the coated LCP part do not change.

Such fluoropolymer coatings are known in the art and are described, for example, in C. P. Izzo, in Hnadbook of Plastics, Elastomers and Compistes, 3rd Ed., CA Harper, Ed., McGraw Hill, New York, 1996, Chapter 6], often assisting in the manufacture of smooth, uniform adhesive coatings. These other materials may be one or more fillers, pigments, one or more other polymers, or other materials. The fluoropolymer coating preferably comprises at least about 10% by weight fluoropolymer, more preferably at least about 25% by weight fluoropolymer, particularly preferably at least about 50% by weight fluoropolymer. Such fluoropolymer coating materials, and any related necessary materials, such as primers, are commercially available from E. I. DuPont de Nemours & Co, Inc., Wilmington, Delaware. These may be powder coatings or dispersions (dispersed in water and / or solvent) coatings. They may also contain more than one type of fluoropolymer. For example, useful coating materials include Teflon® FEP Resin Finish Clear (Resin Finish No. 856-200, EI DuPont de Nemours & Co., Inc., Wilmington, Delaware, USA). Available from).

Coated LCP articles are useful for any use where the surface properties of the fluoropolymers are useful, such as those whose surfaces are chemically inert and whose adhesion to any material that is in contact with them is small, does not cause contamination and should be nontoxic. In particular, such articles are known for the non-tacky nature of fluoropolymers and are useful in chemical process systems where suitable oven containers, inert surfaces are required and frictional properties are low. Among many of these applications, such as oven vessels, the high temperature resistance of the LCP is particularly useful as the substrate material of the article, in which the melting point of the fluoropolymer (s) used for coating is above about 250 ° C. so that it does not melt severely upon use. It is preferable not to. Oven container means an article capable of being cooked and / or heated at a temperature suitable for cooking and / or heating food in a heat and / or ultrasonic oven. The article intended for use in the ultrasonic oven need not be high temperature resistant, where the melting point of the LCP and / or fluoropolymer should preferably be above 150 ° C, more preferably above 200 ° C. In other applications, such as chemical processes, the required melting point of LCP and fluoropolymers is determined by the temperatures reached in the particular application.

Preferably the oven vessel or other part is not completely coated (encapsulated) by the fluoropolymer, but is coated on one or more surfaces. For example, oven vessels are often in the form of bowls or pots, preferably coated only on the inner surface of the bowl or pot. That is, it is particularly desirable to coat only the surfaces that normally come into contact with food or food ingredients during cooking and / or heating. Thus, the fluoropolymer coating is preferably in contact with food or other materials to which the part is exposed. In oven vessel applications and other applications, most foods naturally contain water, so it is particularly important that the fluoropolymer adheres to the LCP even after exposure to water, including boiling water.

Preferred LCP parts to be coated are melt molded, ie injection molded, extruded, melt blow molded, thermoformed and the like. Injection molded parts are preferred LCP parts.

Fluoropolymers useful as coatings include polytetrafluoroethylene, copolymers of tetrafluoroethylene (TFE) such as TFE / perfluoro (propyl vinyl ether), TFE / hexafluoropropylene, TFE / ethylene, and other fluorinated Polymers such as poly (vinyl fluoride) and poly (vinylidene fluoride). Preferred fluoropolymers are polyTFE, TFE / perfluoro (propyl vinyl ether) and TFE / hexafluoropropylene, particularly preferred polymers are TFE / perfluoro (propyl vinyl ether) and TFE / hexafluoropropylene.

LCPs are other materials that are typically melt mixed with such polymers, such as fillers / reinforcers (eg, talc, glass fibers, glass flakes, wollastonite, milled glass fibers, glass beads, calcium sulfate, mica and TiO ₂ ), colorants and pigments (Eg, carbon black and TiO ₂ ), stabilizers such as antioxidants, and other materials. One or more of these materials may be present in conventional amounts. Prior to coating with the fluoropolymer, the LCP can be molded by any conventional method, in particular by injection molding, compression molding, blow molding, extrusion and thermoforming.

In some of the examples, the polymers used comprise 4,4′-biphenol / hydroquinone / terephthalic acid / 2,6-naphthalenedicarboxylic acid / 4 having a composition (repeated unit) of a molar ratio of 50/50 / 87.5 / 12.5 / 300. Hydroxybenzoic acid. Such polymers can be synthesized by the method described in US Pat. No. 5,525,700. In the examples the following materials were used.

Jetfil® 575C Talc: available from Luzenac America, Inc., Englewood, Colorado, USA.

Tiona® RCL4 titanium dioxide: chloride process rutile TiO ₂ surface treated with alumina and organic material, available from SMC Corp., Baltimore, Maryland.

Ultranox® 626: Phosphorus-containing antioxidant, available from GE Specialty Chemicals.

The adhesion of the fluoropolymer coating to the LCP was tested by cutting the fluoropolymer coating with an "X" with a razor blade. A piece of Scotch® Magic Tape # 810 (3/4 "(1.91 cm wide), available from 3M Corp., St. Paul, Minn., USA, was pressed with a finger to include" X ". After application to the site, it was peeled off If the fluoropolymer coating was removed in small amounts or not at all or loosely peeled off, adhesion was considered to be good.

<Example 1>

LCP in a 40 mm ZSK Warner and Pfleiderer twin screw extruder and die with a zone with a conventional transport member, a zone with a kneading or mixing member, and a low pressure zone for evacuating any volatiles from the polymer melt in vacuum The resin was mixed with talc, TiO ₂ , Ultraox® 626 phosphite stabilizer. As the mixed composition exited the die, water was quenched by quenching and cut into pellets using conventional rope cutters. The extruder barrel and die temperature was maintained at about 340 ° C. Prior to molding the pellets, the pellets were dried overnight in a vacuum oven purged with N ₂ at 100-130 ° C. for approximately 16 hours. The LCP composition contained 54.7 wt% LCP, 40.0 wt% Jetfill® 575C talc, 5.0 wt% Thiona® RCL4 TiO ₂ , and 0.30 wt% Ultranox® 626. 6 oz. (171 g) Barrel temperature of 345 ° C, nozzle temperature of 345-350 ° C, mold temperature of 115 ° C, shaft speed of 120 rpm, injection boost of 1.5 seconds, injection of 5 seconds, holding time of 10 seconds and about 3 on a single-axis injection molding machine Molding was made using the mold opening in seconds. The injection boost was 35 MPa, the injection pressure was 28 MPa, and the back pressure was 350 kPa.

Four injection molded discs, 10.2 cm in diameter and 0.16 cm in thickness, were heat aged for 8 hours in a 250 ° C. circulating air oven and then for 30 minutes at 315 ° C. This disc is available from EMC Coating, Inc., Newport, Delaware, USA. EMC-128 coating system (Teflon, EI DuPont de Nemours & Co., Inc., Wilmington, Delaware, USA) ) FEP, thought to contain a copolymer of TFE and hexafluoropropylene having a melting point of about 275 ° C.). This fluoropolymer coating was baked on LCP for 30 minutes at a temperature of 310 ° C. Prior to application of the fluoropolymer, the LCP surface is available from EI DuPont de Nemours & Co., Inc., Wilmington, Delaware, USA, Teflon® Primer Black (Product Code No. 420-703). ). The fluoropolymer coating adhered well to the LCP. One of the disks was immersed in boiling water for 2 hours, after which no change in the appearance of the disk or adhesion of the fluoropolymer to the LCP was seen.

<Example 2>

The polymer used was 4,4'-biphenol / hydroquinone / terephthalic acid / 2,6-naphthalenedicarboxylic acid / 4-hydroxybenzoic acid whose composition (repeated unit) was molar ratio 50/50/85/15/300. Prepared in the same manner as in the LCP of Example 1. It contained 45 wt% glass fibers and 5 wt% TiO ₂ . Plaques 10 cm by 10 cm by 3 mm thick were molded in a similar manner to the plaques of Example 1. Two plaques were heat aged at 250 ° C. in air for 8 hours. One of these plaques was coated with a fluoropolymer as in Example 1 and the other was coated in the same manner except that no primer was used. The third plaque was heat aged for 8 hours at 250 ° C. in nitrogen and coated with fluoropolymer in the same manner. The adhesion of the fluoropolymer coating to the LCP was good at all three plaques.

Claims (4)

Parts made of thermotropic liquid crystalline polymer and coated with fluoropolymer coating. The component of claim 1 which is an oven vessel component. The part according to claim 1 or 2, wherein the fluoropolymer is a perfluoropolymer. The method of claim 3, wherein the perfluoropolymer is a copolymer of polytetrafluoroethylene or tetrafluoroethylene.