JPS6035380B2 - fluorocarbon primer - Google Patents

Description

[Detailed description of the invention] Polytetrafluoroethylene (PTF) is added to the fluoropolymer.
Cookware coated with E) has recently come into widespread use.

Many cooks prefer to use such cookware because of its non-stick properties and because of its ease of cleaning. It is well known that the adhesion of fluoropolymers to metals is rather weak, and therefore, in the manufacture of such cookware, a primer composition is applied to the metal prior to application of the fluoropolymer top coat. It is a common practice to improve the quality.

Such a brimer composition was disclosed in the specification of Patent Application No. 72706 issued on June 18, 1975 (Japanese Patent Publication No. 72706 of 1975).
No. 1756), but its composition is (
a} fluoropolymer, 'b) a binder consisting of colloidal silica and an amine salt of a polyamic acid, a W flocculant, and [d) a liquid carrier. Although cookware subbed with such compositions is very durable, the overall fluoropolymer coating tends to become scratched after long-term use.

According to the invention, it has been found that the scratch resistance of such coatings is improved if the primer composition contains step-mother particles, pigment-coated mica particles or metal flakes.

The mica particles, coated mica particles and metal flakes used in the compositions of the invention can be any commercially available.

These particles and flakes have an average longest dimension of 10 to 200 microns, preferably 15 to 50 microns, with up to 50% of the particles or flakes having a longest dimension of about 500 microns or more. Particle and flake sizes are measured optically against standards. A more preferred pigment-coated mica particle for use is U.S. Pat. No. 3,087,827.
No. 3,087,828 and No. 3,087,829.

The disclosures of these US patents are mentioned herein by reference for various coated micas and methods of their preparation. The mother-in-law described in said US patent is coated with an oxide or hydroxide of titanium, zirconium, aluminum, zinc, antimony, tin, iron, copper, nickel, cobalt, chromium or vanadium.

Titanium dioxide coated mica is more preferred due to its availability. Mixtures of coated micas can also be used. Typical examples of metal flakes that can be used include, for example, aluminum flakes, stainless steel flakes, nickel flakes and bronze flakes.

Mixtures of these flakes can also be used. Mica, coated mica or metal flakes are usually
about 0.2 to 2 weight percent of total solids, preferably about 2 to 1
It is present in the compositions of the invention at a concentration of 5% by weight, more preferably from about 5 to IZ% by weight.

By "total solids" is meant the sum of the fluoropolymer, mica, coated mica or metal flakes, polyamic acid salts, pigments and colloidal silica content. The fluoropolymers used in the compositions of the invention are homopolymers of monoethylenically unsaturated hydrocarbon monomers completely substituted with fluorine atoms or with a combination of hydrogen atoms and chlorine atoms. and copolymers (meaning that the polymer contains two or more different monomer units).

This group includes, for example, perfluoroolefin polymers such as polytetrafluoroethylene and copolymers of tetrafluoroethylene and hexafluoropropylene in any monomer unit weight ratio, such as polymonochlorotrifluoroethylene. Fluorochlorocarbon polymers, and tetrafluoroethylene and perfluoroalkyl vinyl ethers (where the alkyl group is 1 to 5
normally solid copolymers with carbon atoms (consisting of Mixtures of these can also be used. P.T.
FE is preferred due to its thermal stability. The fluoropolymer used is in particulate form. Preferably, the particles are small enough to pass through the nozzle of the spray gun without blocking them, yet also small enough to impart integrity to the resulting film. The fluoropolymer has a molecular weight of at least about 20,000, more preferably at least about 2,000.
Preferably, it has a number average molecular weight of 0.00.

For some reason, it takes fluo. This is because polymers provide a harder coating. The number average molecular weight of PTFE is
mal of Applied PoIMmerScie
nce'', Vol. 17, pp. 3253-325 (1973). The number average molecular weight of a polytetrafluoroethylene/hexafluoropropylene copolymer is determined by first determining its melt flow rate (MFR) according to ASTM D2116, and then using the following formula MV = stroke x working pressure. (side) x orifice radius (side 2
It is determined by determining the melt viscosity MV according to 8×MFR×orifice length (side) and then determining the molecular weight MW according to the following formula MV MW=3·41.62×lo-13.

The number average molecular weight of fluorochlorocarbon polymer is AST
Measured by MD1430. Although powders of fluoro-polymer can be used and the carrier can be provided separately,
Polymers in the form of aqueous dispersions are preferred because of their stability and because they are most easily obtained in that form. The fluoropolymer is typically present in the composition at a concentration of about 10-90%, preferably about 60-80% of the total weight of fluoropolymer and binder (as defined below).

The binder in the composition of the invention consists of colloidal silica and an amine salt of a polyamic acid.

The binder is typically present in the composition at a concentration of about 10-90%, preferably about 20-40% of the total amount of fluoropolymer and binder. The colloidal silica component of the binder can be any that produces a continuous film when air-dried and allowed to sit on its own.

Such silica is generally provided in the form of an aqueous sol containing about 30-5% by weight colloidal silica. Specific examples of colloidal silica sol that can be used include "Redox HS-40" (registered trademark), "Rudox SM-30" (registered trademark), "Rudox HS" (registered trademark), and "Rudox TM" (registered trademark). ), “Ludox B” (registered trademark), “Ludox AM” (registered trademark)
, and those sold by DuPont as "Ludox AS" (registered trademark).

A more preferred colloidal silica sol is “Ludox AM
” (registered trademark).

This product has a pH of about 9 and 30 at 25°C.
sodium-stabilized colloidal silica with a silica content (calculated as Si02) of 13%, the particles are surface-modified with aluminum and
Particle diameter of 14 mm microso and 210 per gram
It has a specific surface area of ~23 pi square meters. Mixtures of colloidal silica can also be used. Colloidal silica usually about 5 to 95% by weight of binder, preferably about 1
Present in the binder at a concentration of 0-80%. The polyamic acid salt component of the binder may be any of those described in Idenuka Patent Kao No. 10457 (Japanese Patent Publication No. 571-10897) dated February 4, 1975.

Generally speaking, the polyamic acid salts used in the compositions of the present invention are salts of polyamic acids with tertiary amines. Polyamic acids have the following structural formula (where G is hydrogen or a carboxyl group, → means isomerism, R is a tetravalent organic group containing at least 2 carbon atoms, and the 2 not more than four carbonyl groups are bonded to any one carbon atom of the tetravalent group, R, is a divalent group containing at least two carbon atoms, and each adjacent polyamic acid unit the amide group of is bonded to another atom of the divalent group, and n
is a number large enough to give the polyamic acid an intrinsic viscosity of at least 0.1 when measured as a 0.5% solution in N,N-dimethylacetamide at 30q0)
It can be expressed as

These polyamic acids are neutralized with stoichiometric amounts of tertiary amines to give amine salts. More preferred amine salts of polyamic acids for use in the binder component include at least one amine having the structure 2N-R, -NH2 and a compound having the structure 2N-R, -NH2, where R and R are and at least one type of acid anhydride represented by the following definition:

Particularly preferred amine salts of polyamic acids for use in the binder component are ○) metaphenylenediamine or paraphenylenediamine, bis(4-aminophenyl)ether, benzidine, 2,2-bis(4'-aminophenyl)propane. , bis(4-aminophenyl)methane,
Bis(4-aminophenyl) sulfone, bis(4-aminophenyl) sulfide or 1,6-hexamethylene diamine, and ■ pyromellitic dianhydride, trimellitic anhydride, 2,2-bis(3,4'-dicarboxyphenyl) prepared from propane dianhydride or bis(3,4-dicarboxyphenyl) ether dianhydride and then containing stoichiometric amounts of trimethylamine, triethylamine, dimethylethanolamine, diethyl 2-hydroxyethylamine, tributylamine, tris(2-hydroxy ethyl)amine, ethylbis(2-hydroxyethyl)amine, N,N-dimethylaniline, morpholine,
It is obtained by neutralizing with pyridine, N-methylpyrrole or a mixture thereof.

The most preferred polyamic acid salt for use in the binder component is prepared from bis(4-aminophenyl)methane and trimellitic anhydride, which is then combined with stoichiometric amounts of triethylamine and diethyl 2-hydroxyethylamine. It is obtained by neutralizing with a mixture with a weight ratio of 2/.

The amine salts are usually present in the binder at a concentration of about 5-95% by weight of the binder, preferably about 20-9%.
The coalescing agents used in the compositions of the present invention are generally organic liquids capable of dissolving the polyamic acid amine salts used.

This type of organic liquid is very polar and has a polarity of 10,000
or higher boiling point. Specific examples include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethinoresulfoxide, cresylic acid, sulfolane and formamide. The preferred luting agent for use due to its ready availability and low toxicity is N-
It is methylpyrrolidone.

The luting agent is about 10% of the commonly used polyamic acid amine salt.
It is present in the compositions of the invention at a concentration of ˜9% by weight, preferably about 20-5% by weight. The compositions of this invention contain about 15-20% of the polyamic acid amine salt in which they are used.
preferably about 80-15% by weight of a viscosity reducing agent, which has a solubility parameter 6T of 10-21.6.
and are miscible with water)
will have a more manageable viscosity at higher solids content.

Definitions of solubility parameters are given in Encyclopedia of Chemical Technology, edited by Kirk Osmer, 2nd edition (1963), pages 889-896. The total solubility parameter T is the following component parameter, namely the dispersion component 6o 7.0 to 1
0.0 facultative component 6P 2.0~1
1.0 Hydrogen bond component 7.0-14
．． 0, where the equation 8T2 = 6D2 6P2 6 day 2 describes the relationship of each component to the total solubility parameter.

Specific examples of such viscosity reducing agents include, for example, furfuryl alcohol, 1-butanol, 2-pro/gnol, ethylene glycol monoethylenal, triethylene glycol, formic acid and mixtures thereof. Furfuryl alcohol is more preferred due to its effectiveness. The compositions of the invention can also contain conventional additives, such as pigments, flow control agents, surfactants and plasticizers, if necessary or desirable.

These additives are added in the usual manner and in the usual amounts for the usual reasons. The carrier used in the compositions of the invention can be any of those commonly used in compositions of this type.

it is an inert, non-reactive or non-active (in the sense of contributing to the action of the invention) component;
Therefore, its nature is secondary. The carrier serves merely to keep the composition homogeneous and acts as a mechanism for transporting the solid components to the substrate. After the coating has been deposited, the carrier is evaporated. It therefore only needs to be compatible with the other components of the composition and not have an adverse effect on the coating itself. Generally, the fluoropolymer used in the composition is provided in the form of an aqueous dispersion, and the water that is introduced into the composition with the polymer also serves as all or part of the carrier for the composition. .

It is also possible to use, for example, alcohols, ketones, aliphatic and aromatic hydrocarbons or mixtures thereof.
The amount of total solids in the coating composition is governed by factors such as the substrate to which the composition is applied, the method of application, and the curing operation.

Typically, the composition will contain about 10-8% solids by weight. The compositions may be prepared by simply mixing together appropriate amounts of each appropriate component.

If a pigment is desired, it can be added by first conventionally preparing a suitable pigment dispersion and then adding this dispersion to the composition. The resulting compositions may be applied by spraying, brushing, roll coating, dipping or lightning coating.

The substrate is preferably pretreated by grit spraying, metal or metal oxide flame spraying, or frit coating, although the compositions may also be applied to phosphated and chromated metals. The compositions of the present invention are typically applied to a thickness (dry) of about 2 to 15 microns and then air dried.

This subbing coating is then overlaid with a conventional clear or pigmented fluoropolymer enamel and baked in conventional manner to provide an adhesive fluoropolymer coating.
Although the best coatings are obtained with the dual coating system described above, strongly adhesive fluoropolymer coatings are obtained in a single application operation.

This is accomplished by applying a coating of the composition of the invention to a thickness (dry) of 5 to 50 microns. The coating is then air dried and baked at a temperature high enough to melt the fluoropolymer used. The compositions of the present invention are most useful for priming metal cookware, particularly frying pans, prior to coating with PTFE, but the compositions are also useful for coating other metal cookware requiring a tightly bonded fluoropolymer coating. It can also be used for subbing products.

These other products can be made from glass or any other material that can withstand the baking temperatures used. For example, the compositions can be used in bearings, valves, electrical wires, metal foils, boilers, pipes, boat bottoms, oven linings, iron soles, waffle irons, ice trays, snow shovels and plows, chutes, shovels, dies, such as saws, files and drills. It can be used to underline or coat tools such as tools, hoppers and other industrial containers, and molds. Next, the present invention will be explained by examples.

All parts and percentages in this example are by weight unless otherwise indicated. EXAMPLE The following ingredients were added to a vessel in the order listed and mixed.

{1} Polyamic acid amine salt solution (prepared as described below) 31.98 parts {2) Furfuryl alcohol 3.21 parts (3} Deionized water 109.47 parts [4- Pigment dispersion liquid 27.3 $ parts (prepared by ball milling a mixture of 45 parts cobalt oxide and 55 parts water) (5} Ti02 coated mica 7.6
(“Afflain” (registered trademark) NF-152-D
- DuPont commercial product) Ingredients {Added immediately with vigorous mixing.

After the addition was complete, the product was stirred for 10 minutes. The following were then added to it while mixing. '6} 91.17 parts of PTFE dispersion (60% solids in water, commercial product manufactured by DuPont, "Teflon" (registered trademark) TFE-fluorocarbon resin, aqueous dispersion T-30 {71 Ludtux AM 36.78
The resulting primer composition was sprayed onto a degreased aluminum panel to a thickness of about 8 microns (dry) and then air dried.

The topcoat composition was prepared by adding the following to a container in the order listed while mixing.

{B'[81 PTFE dispersion liquid on the above side 179
．． 7 parts '9' Deionized water 2.7
Part [10 Mica coated with Tj02 of '51 9
．． 5 parts (11) Pigment dispersion liquid of the above 3.5
Part (12) 11.24 parts of toluene, 14.78 parts of trietanoamine, 4.27 parts of butyl carbitol, 4.72 parts of oleic acid, 2.88 parts of cerium octoate solution (12% in 2-ethylhexanoic acid), A mixture consisting of 1.61 parts of "Triton Tripolymer Dispersion (40% in Water) The resulting topcoat composition was exposed onto an air-subbed panel to a thickness of about 20 microns.

The panels were then phosphorized at 42500 for 5 minutes. The resulting finish exhibited significantly better scratch resistance than that containing no coated mica component. The polyamic acid amine salt solution used in this example was prepared as follows.

Claims (1)

[Claims] 1. Components (a) to (e) below, namely (a) (a)
) and (b) of about 10 to 90% of the combined weight of the solids of monoethylenically unsaturated hydrocarbon monomers completely substituted with fluorine atoms alone or in combination with fluorine atoms and chlorine atoms. (b) about 10 to 90% of the combined solids weight of (a) and (b), (1) (1) and (2);
from about 5 to 95% of the combined weight of the solids of colloidal silica which itself air-dries to form a continuous film when left to dry; and (2) the combined weight of the solids of (1) and (2). about 5-95% of the structure neutralized with a stoichiometric amount of a tertiary amine. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, G is hydrogen or carboxyl group, → means isomerism, R is a tetravalent organic group containing at least 2 carbon atoms, and each polyamic acid not more than two carbonyl groups of the unit are bonded to any one carbon atom of the above tetravalent group, R_1 is a divalent group containing at least 2 carbon atoms, and R_1 is a divalent group containing at least 2 carbon atoms, and the adjacent polyamic acid units Each amide group is bonded to another atom of the divalent group, so that n is at least 0 when measured as a 0.5% solution in N,N-dimethylacetamide at 30°C.
．． (c) a binder consisting of a salt of a polyamic acid having a number sufficiently large to give the polyamic acid an intrinsic viscosity of 1, based on the weight of the polyamic acid amine salt;
0-90% N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide,
Cresylic acid, sulfolane or formamide, (d)
A primer composition comprising about 0.2-20% of the combined weight of (a) and (b) mica particles, pigment-coated mica particles or metal flakes, and (e) a liquid carrier. 2. The composition of claim 1, wherein the colloidal silica is sodium stabilized colloidal silica. 3 The polyamic acid salt contains at least one amine represented by the structural formula H_2N-R_1-NH_2 and the structural formula ▲
There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. A composition according to claim 1, which is prepared from an acid anhydride of a species and obtained by neutralizing it with a stoichiometric amount of a tertiary amine. 4 The polyamic acid salt is (a) meta-phenylenediamine or para-phenylenediamine, bis(4-aminophenyl) ether, benzidine, 2,2-bis(4'-aminophenyl)propane, bis(4-aminophenyl) Methane, bis(4-
aminophenyl) sulfone, bis(4-aminophenyl) sulfide or 1,6-hexamethylenediamine,
and (b) pyromellitic dianhydride, trimellitic anhydride, 2,2-bis(3',4-dicarboxyphenyl)
Propane dianhydride or bis(3,4-dicarboxyphenyl)ether dianhydride. A composition according to claim 3, which is obtained by neutralizing it with a stoichiometric amount of a tertiary amine. 5. The composition according to claim 1, wherein the fluorocarbon polymer is PTFE. 6. The composition according to claim 1, wherein the carrier is water. 7. The composition according to claim 1, wherein component (d) is mica particles coated with TiO_2. 8 Manufactured from (a) PTFE, (b) colloidal silica stabilized with sodium, (c) trimellitic anhydride and bis(4-aminophenyl)methane, which is combined with triethylamine and diethyl 2-hydroxyethylamine. /_1 weight ratio combination of a polyamide salt obtained by neutralization, (d) mica coated with TiO_2, and (e) water as a carrier. Composition.