Protective graft coating for application onto polyurethane for chemical resistance, stain resistance, abrasion resistance and U.V. resistance

Abstract

This invention relates to a coating comprising prepolymer and monomers for application onto polyurethane for chemical resistance, abrasion resistance, water proof etc. Usually polyurethane is porous and does not have sufficient stain, abrasion and chemical resistance. The said coatings developed using technology of chemical grafting that involves the use of prepolymers, monomers, catalyst, graft initiator, wetting agents, fillers and other ingredients of the composition. The coating thus obtained when applied on the polyurethane allows obtaining graft polymerization, thereby forming a polymeric film chemically attached to the substrate. The polyurethane substrate is reacted with craft initiator which creates the reaction sites on the substrate via free radical mechanism. This in turn renders the substrate receptive to attachment of monomers/prepolymers forming polymeric film that is chemically bonded to the substrate which has then the desired property in terms of stain resistance, abrasion wear, crock, water, chemical resistance and other properties.

Claims

1. A method of grafting a coating onto a substrate comprising: a) preparing a mixture of: a solvent including water, (ii) a UV resistant compound, (iii) a surfactant, (iv) a monomer, (v) a urethane prepolymer, (vi) Fluoroethylene-alkyl vinylether (FEVE) alternating copolymer and (vii) a graft initiator to define an admixture of monomers and prepolymers, and (c) applying the admixture onto the substrate.

2. The method of claim 1 wherein said admixture is sprayed onto said substrate.

3. The method of claim 2 further comprising drying said sprayed admixture for about 10 to 15 minutes and subjected to a cure of 125 to 150 degrees centigrade for about 5 to 10 minutes.

4. The method of claim 3 wherein said admixture comprises a first component that has a functional group for reaction and covalent bonding with an active site for the substrate.

5. The method of claim 4 wherein the first component is a water dispersible polymer.

6. The method of claim 5 wherein said water dispersible polymer comprises an epoxy prepolymer, a urethane prepolymer and an acrylic prepolymer.

7. The method of claim 6 wherein said water dispersible polymer includes at least one functional group selected from carboxyl, hydroxyl, epoxy, amino, melamine, acrylic group and fluoro group.

8. The method of claim 1 wherein said monomer is selected from the group consisting of acrylate, methacrylate, or urethane acrylate.

9. The method of claim 1 wherein said graft initiator is a metallic salt.

10. The method of claim 9 wherein said metallic salt is selected from the group consisting of silver nitrate, silver perchlorate, ferrous ammonium sulfate, and silver acetate.

11. The method of claim 10 including a catalyst selected from the group consisting of peroxide of urea, hydrogen, and benzoyl.

12. The method of claim 1 wherein the solvent includes butyl carbitol.

13. The method of claim 1 wherein the admixture composition comprises: TABLE-US-00004 PARTS BY FORMULATION WEIGHT Bulyt Carbitol 40.00 ethyl 3-ethoxy propionate Solvent 20.00 Antioxidant pentaerythritol tetrakis[3-[3,5- di-tert- 0.08 butyl-4-hydroxyphenyl]propionate] UV absorber 0.08 Non ionic surfactant 2.00 octophenolpoly(ethyleneglycolether) 3,4-(epoxycyclohexyl)ethyltriethoxysilane 8.00 Water 320.00 Silica Flattening Agent 16.00 Silica modified Acrylic dispersion mixture of acrylic 200.00 polymers 18-19% , residual monomers <500 ppm, water 74-77% and amorphous silica 5-8% Urethane Prepolymer 120.00 Fluoroethylene-alkyl vinylether (FEVE) alternating 160.00 copolymer modified poly vinylidene fluoride dispersion 160.00 fluoro emulsion 24.00 polyterafluoroethylene dispersion 20.00 50% in water Melamine Prepolymer 24.00 Ethoxylated(15)trimethylolpropanetriacrylate 4.00 Dodecyl Benzene Sulfonic Acid catalyst 1.00 Urea Peroxide 1.00% Solution in Water 0.20 Silver Perchlorate 0.1% Solution in Water 0.2.

14. The method of claim 1 wherein the admixture composition comprises: TABLE-US-00005 PARTS BY FORMULATION WEIGHT Bulyt Carbitol 10.00 ethyl 3-ethoxy propionate Solvent 5.00 pentaerythritol tetrakis[3-[3,5- di-tert-butyl-4- 0.20 hydroxyphenyl]propionate] UV absorber 0.20 Non ionic surfactant octophenolpoly 0.50 (ethyleneglycolether) 3,4-(epoxycyclohexyl)ethyltriethoxysilane 2.00 vinyltrimethoxysilane 0.50 Silica Flattening Agent 5.00 mixture of acrylic polymers 18-19%, residual 54.00 monomers <500 ppm, water 74-77% and amorphous silica 5-8% Fluoroethylene-alkyl vinylether (FEVE) alternating 55.00 copolymer modified poly vinylidene fluoride dispersion 30.00 mixture of acrylic polymers 18-19% , residual 04.00 monomers <500 ppm, water 74-77% and amorphous silica 5-8% polyterafluoroethylene 10.00 dispersion 50% in water Melamine Prepolymer Methylated melamine 06.00 formaldehyde resin Water 80.00 Ethoxylated(15)trimethylolpropanetriacrylate 4.00 Fluoro Emulsion fluoro surfactant 10.00 Urea Peroxide 1.00% Solution in Water 0.20 Silver Perchlorate 0.1% Solution in Water 0.20.

15. The method of claim 1 wherein the admixture composition comprises: TABLE-US-00006 PARTS BY FORMULATION WEIGHT Bulyt Carbitol 10.00 Antioxidant pentaerythritol tetrakis[3-[3,5- di-tert- 0.08 butyl-4-hydroxyphenyl]propionate] UV absorber 0.08 Non ionic surfactant octophenolpoly 2.00 (ethyleneglycolether) 3,4-(epoxycyclohexyl)ethyltriethoxysilane 8.00 Dispersing Agent 2.00 Water 320.00 Silica Flattening Agent 16.00 mixture of acrylic polymers 18-19% , residual 20.00 monomers <500 ppm, water 74-77% and amorphous silica 5-8% Urethane acrylic prepolymer 40.00 Fluoroethylene-alkyl vinylether (FEVE) 80.00 alternating copolymer 2% Solution of fluoro surfactant in Water 2.00 Acrylic fluoro emulsion 24.00 polyterafluoroethylene dispersion 50% in 10.00 water Melamine Prepolymer fluoro dispersant 20.00 Methylated melamine formaldehyde resin Urethane Acrylate SR 9035 monomer 4.00 Urea Peroxide 1.00% Solution in Water 0.20 Ferrous Ammonium Sulfate 0.1% Solution in 0.20. Water

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) Mechanism

(2) Many materials, both naturally occurring and synthetic possess hydrogen which are more reactive than the “bulk hydrogens”, for example, the tertiary hydrogen in polypropylene I, the amide hydrogen in proteins II and hydroxyl hydrogen n polysaccharides III.

(3) ##STR00001##

(4) The chemical activator (C.A.) has the capacity of removing these active hydrogens and concomitantly initiating the growth of polymer chains at the site from where the active hydrogen was removed. In the case of polypropylene, this can be represented as follows:

(5) ##STR00002##

(6) Where X can represent either a free radical, anion or cation, depending on whether the graft initiators (G.I.) removes a hydrogen and one electron, no electrons or two electrons, respectively. (There are a wide variety of monomers which do not lend themselves to the free-radical type of polymerization).

(7) ##STR00003##

(8) where “X” governs the property or properties that are obtained. In many instances a mixture of monomers is employed and often more than one property can be altered in one processing step. These polymer chains, whose length can be controlled, are permanently attached to the “substrate”. The linkage between the graft-polymer and the substrate is covalent in nature, therefore, the graft-polymer cannot be leached from the substrate,

(9) In addition to these types of materials, substrates which ordinarily would not be considered as possessing “active hydrogens” such as silicon, metals, polycarbonate sites for attachment are provided, where possible, by the removal of a hydrogen from the substrate or by the removal of liable electrons which are available from the bulk of the material.

(10) General Mechanism for Grafting onto a Substrate

(11) Chemical grafting comprises growing polymer chains on a backbone chain of a substrate. The graft polymer chains are formed from vinyl monomers containing appropriate functionability, e.g. groups such as hydroxyl, carboxyl, epoxy, amide, amine, anhydride, etc. The series of steps involved in the mechanism of chemical grafting to produce grafted polymer chains on the vinyl substrate, represented below:

(12) ##STR00004##

(13) (Regeneration of the Chemical Activator and Free Radical)

(14) This process may be terminated by radical combination.

(15) ##STR00005##

(16) Reaction 6 especially should give a chemical bridge between the substrates, The side functional group .X could be chosen such that their further interaction with the substrate shall result into desired properties, e.g. adhesion, barrier properties and other characteristics.

(17) The graft initiator ion starts the action and the whole process behaves like an anticatalytic one. A small amount of graft initiator ion (5 to 10 ppm) is therefore sufficient to carry out the process of graft polymerization. All of the foregoing reactions take place in the presence of peroxide which concurrently regenerates the graft initiator forming a free radical.
GI+ROOH.fwdarw.RO+OH.sup.−+GI.sup.+

(18) In the case of polyester, it is presumed the reaction takes in the following way:

(19) ##STR00006##

(20) The free radical carbonyl group thereafter reacts with either a first component or a second component (e.g.

(21) ##STR00007##

(22) ##STR00008##

(23) The process may be terminated by radical combination.

(24) ##STR00009##

(25) Chemical Grafting on Urethane/Polyurethane

(26) The chemical grafting of polyurethane can be described by the following reactions:

(27) ##STR00010##

(28) Further Discussion

(29) In this description graft-initiation is portrayed as being separate and distinct from the subsequent graft-polymerization. For some applications this is the case. However, for a majority of the uses these steps can be combined due to the fact that the graft initiators possess sufficient selectivity such that almost no homopolymer is encountered.

(30) This is true for the situation where the desired end result could be obtained by the attachment of a commercially available vinyl monomer. But there are cases where such a monomer is not available or where it might be advantageous to have a substance relatively loosely bonded (so as not to inactivate a functional group or destroy a particular conformation). Three approaches are possible for this type of situation:

(31) A. Through a covalent linkage—Monomers of the acrylic acid type can supply a “handle” which allows for the attachment of the desired species to a substrate. If the species contains a hydroxyl group (either alcoholic or phenolic-A-OH),

(32) ##STR00011##

(33) However, if it contains an amino group (R-NHR/),

(34) ##STR00012##

(35) Finally, if it contains a carboxyl group (R-C( ),

(36) ##STR00013##

(37) The rate of release of the desired species is governed by the kinetics for hydrolysis of classical esters and amides,

(38) B. Through an electrostatic bond—Permanent positive or negative charges can be introduced onto substrates by the use of monomers which contain permanent positive or negative charges.

(39) a. Positive Charges

(40) Many examples of quaternary-nitrogen-containing vinyl monomers are known or are readily available, e.g. benzyl 2-methyl-5-vinylpyridinium chloride,

(41) ##STR00014##

(42) Substitution on the pyridine ring in various positions with both electron-donating and electron-accepting groups would provide for a series of vinyl monomers with a variety of strengths of positive charge. Another family could be obtained from vinyl anilinium salts,

(43) ##STR00015##

(44) b. Negative charges

(45) Families of vinyl monomers which contain salts of acids are known or may be readily synthesized, e.g., the vinyl benezenesulfonic acids:

(46) ##STR00016##

(47) When permanently attached to a substrate, these monomers result in a permanently negatively charged surface.

(48) In these instances, if the desired species has any positive or negative polarity whatsoever, it can be attached to a substrate of opposite polarity. Also, the judicious selection of the polar monomer attached to the substrate would allow for different strengths of attachment and therefore subsequent release, should this be desirable.

(49) C. Through hydrogels introduced onto various materials—Hydrogels generally fall into two categories, hydroxyalkyl derivatives of acrylic or methacrylic acid and acrylamides. These highly swollen hydrogels are quite weak physically and generally it is advantageous to chemically graft them onto a substrate. The desired species are held to the hydrogel by Van der Waal's forces. Thus, the activity of an enzyme for example can be maintained in this type of system because both its active site and its conformation is unaltered. Release of the desired species is diffusion controlled.

(50) Polyurethane may be defined as a polymer containing a plurality, carbonate linkages. The term polyurethane has also come to be used as a general name for the segment of the plastic industry which manufactures or uses polyisocyanates. A foundation of the polyurethane industry is the isocyanate. The physical form and properties of the polymer can also be tailored by selecting from among a broad range of monomers or attaching monomers by chemical grafting.

(51) Generally speaking the chemical and structural diversity of the diverse materials that are called polyurethanes is broad so that it is difficult to describe them in terms of nominal or average properties. Combinations of properties that compare very favourably with those of engineering resins or monomers can be obtained with isocyoanate based polymers. Key polyurethane markets and applications include building and construction appliances, transportation, composite wood, recreation equipment, furnishings, coatings, adhesives, sealants elastomers, marine, medical and apparel.

(52) Polyurethanes can be found in virtually any industry where performance is critical, whether it is through safe guarding efforts of protective coatings. Polyurethane coatings and sealants protect bridges, cars, airplanes etc. Polyurethanes should be the material of choices for applications needing designs freedom and dependable performance. Outdoor and recreation applications will continue to benefit from polyurethane's unique engineered characteristics. Innovative applications will also be found globally in high-tech medical instruments, hospitals and pharmaceutical labs from treatment of trolleys to operating microscopes.

EXAMPLES

(53) The invention described herein can be applied to any number of polyurethane parts to toughen the surface. In one embodiment the invention has particular application to the hospital environment where the surface of beds or chairs are routinely cleaned and sanitized. However over time many of the exterior surface of chairs, beds or the like break down or become cracked, which become breeding grounds for bacteria, viruses and the like to grow. The surface of such chairs, armrest, beds or the like in some cases are comprised of polyurethane. The polyurethane may be a solid continuous surface. In other cases the surface may be comprised of a different material, such as, nylon or vinyl or the like where a polyurethane coating is applied thereon. In each of these cases there is a polyurethane substrate.

(54) In an embodiment of this invention the methods require a grafting solution comprised of water, a catalyst for activating a graft initiator, a graft initiator which renders the substrate receptive to chemical grafting or bonding. The grafting solution also includes at least one monomer or prepolymer or an admixture thereof.

(55) Generally speaking a monomer is a component having a molecular weight of less than 1200. It is especially preferred that at least one monomer has a molecular weight of from about 200 to 800. The prepolymer would have a molecular weight that would be greater than 1200.

(56) The graft solution includes a graft initiator in order to provide an active site on the substrate for reaction. The graft initiator is selected to abstract an active hydrogen as previously described.

(57) In a preferred embodiment the initiator is a metal ion provided by the ionization of a metal salt. When a salt such as a silver nitrate is utilized to activate the graft initiator such salts are preferably present in the graft solution in an amount from about 0.001% to about 0.01% by weight of the solution.

(58) In an embodiment of the invention the graft solution includes a catalyst in order to ionize the metal salts to provide an activating ion. A wide variety of catalysts may be utilized in the method of the present invention including peroxide, peracid or a perbenzoate. Peroxide catalysts of urea, hydrogen and benzoyl peroxides are especially preferred. The catalyst is also present in a small amount. In one embodiment the grafting solution comprises 0.001 to about 0.01% weight of the catalyst.

(59) In an embodiment of the invention the grafting solution would comprise an effective weight percentage of monomer and or prepolymer to provide a tough protective coating having a selected abrasion resistance. For example the grafting solution comprises from about 40 to 50 percent solids in an aqueous solution. Once dried and cured as described herein the protective surface comprises the chemically bonded monomer or prepolymer bonded to the polyurethane substrate backbone.

(60) Method of Preparation of Formulation

(61) A requisite amount of different precalculated quantity of styrene acrylic prepolymers, urethane prepolymers, epoxy prepolymers, acrylic prepolymers, pigments, coupling agents, thickeners, monomers surfactants, water, solvent, catalyst and graft initiator were taken in a container. The coating solution thus prepared is ready for application on the polyurethane substrate.

(62) Method of Application of the Formulation

(63) The coating formulation thus prepared is applied to the polyurethane substrate by spraying or any other convenient method. The coated polyurethane is air dried for 10-15 minutes and subjected to cure at 125-150° C. for 5-10 minutes. It should be noted that the following represent some examples and are not limiting. In other words it is possible to vary some of the ingredients and still obtain the desired results. Again as an example some of the ingredients may be changed by +/−15% or +/−10% and still obtain the desired results.

a) Example I

(64) TABLE-US-00001 PARTS BY FORMULATION WEIGHT Bulyt Carbitol 40.00 EEP Solvent 20.00 Antioxidant Irganox 1010 0.08 U.V. Absorbent Tinuvin 292 0.08 Non Ionic Surfactant Triton X-100 2.00 Monomer Coatosil 1770 8.00 Water 200.00 Flattening Agent Dapro FA-34 16.00 -- Mix the above together then add one by one and mix the following . . . Silica modified Acrylic Prepolymer Chemtan AC-1 200.00 Urethane Prepolymer Urotuf W 38 120.00 Fluro Prepolymer Lumiflon FE 4300 80.00 Fluro Propolymer Lumiflon FE 4400 80.00 Acrylated Polyvinylidene Fluroide Prepo, Kynar Aquatic ARC 160.00 Acrylic Emulsion API 296 E 24.00 Fluro Dispersion AQ 50 20.00 Melamine Prepolymer Cymel 385 24.00 Water 120.00 Urethane Acrylate SR 9035 4.00 Dodecyl Benzene Sulfonic Acid Nacure 5225 1.00 Urea Peroxide 1.00% Solution in Water 0.20 Silver Perchlorate 0.1% Solution in Water 0.2

(65) An effective amount of the above identified chemicals is added to the mixture to obtain the desired properties. The chemical by weight referred to above can vary up to +1-15%

(66) Generally speaking if more of a chemical is added relative the water the thicker, or more viscous the application.

b) Example II

(67) TABLE-US-00002 PARTS BY FORMULATION WEIGHT Bulyt Carbitol 10.00 EEP Solvent 5.00 Antioxidant Irganox 1010 0.20 U.V. Absorbent Tinuvin 292 0.20 Non Ionic Surfactant Triton X-100 0.50 Monomer Coatosil 1770 2.00 Monomer Silane A171 0.50 Flattening Agent Dapro FA-34 5.00 -- Mix the above together then add one by one and mix the following . . . Silica modified Acrylic Prepolymer Chemtan AC-1 54.00 Fluro Prepolymer Lumiflon FE4300 30.00 Fluro Propolymer Lumiflon FE4400 25.00 Acrylated Polyvinylidene Fluride Prepo, Kynar Aquatic 30.00 ARC Silicon Modified Chemtan FA-22 04.00 Fluro Dispersion AQ 50 10.00 Melamine Prepolymer Resimene 717 06.00 Water 80.00 Urethane Acrylate SR 9035 4.00 Fluro Emulsion Rainoff FC-6 10.00 Urea Peroxide 1.00% Solution in Water 0.20 Silver Perchlorate 0.1% Solution in Water 0.20

(68) An effective amount of the above identified chemicals is added to the mixture to obtain the desired properties. The chemical by weight referred to above can vary up to +/−15%. Generally speaking if more of a chemical is added relative the water the thicker, or more viscous the application.

c) Example III

(69) TABLE-US-00003 PARTS BY FORMULATION WEIGHT Bulyt Carbitol 10.00 Antioxidant Irganox 1010 0.08 U.V. Absorbent Tinuvin 292 0.08 Non Ionic Surfactant Triton X-100 2.00 Monomer Coatosil 1770 8.00 Dispersing Agent Irgosperse 2176 2.00 Water 200.00 Flattening Agent Dapro FA-34 16.00 -- Mix the above together then add one by one and mix the following . . . Silica modified Acrylic Prepolymer Chemtan AC-1 20.00 Urethane Prepolymer Neopac E125 40.00 Fluro Prepolymer Lumiflon FE 4300 80.00 2% Solution of FC 4430 in Water 2.00 Acrylic Emulsion API 296 E 24.00 Fluro Dispersion AQ 50 10.00 Melamine Prepolymer Resimene AQ7551 20.00 Water 120.00 Urethane Acrylate SR 9035 4.00 Urea Peroxide 1.00% Solution in Water 0.20 Ferrons Amm. Sulfate 0.1% Solution in Water 0.20

(70) An effective amount of the above identified chemicals is added to the mixture to obtain the desired properties. The chemical by weight referred to above can vary up to +/−15%. Generally speaking if more of a chemical is added relative the water the thicker, or more viscous the application.

Discussion of Invention

(71) According to the method and article of the present invention, chemical and abrasion resistant urethane seats are produced which are better than the conventional product, having improved UV resistance and a composition having improved shelf life. The resulting article or part also exhibits improved physical properties and an enhanced ability to withstand staining and improved U.V. resistance as compared to the prior art and as compared with applicant's US Published 2014/0335362.

(72) The resulting coating layer admixture of the prepolymer and monomer can be varied depending on how far the reaction is carried out. The graft solution includes water, a graft initiator for activating sites on the polyurethane, a catalyst for activating or regenerating the graft initiator and a first component that has a functional group for reaction and covalent bonding with an active site for the substrate. If preferred it can be a water dispersible polymer such as for example an epoxy prepolymer, a urethane prepolymer and acrylic prepolymer. It is preferred that components comprises at least one water dispersible polymer which included at least one functional group, e.g.—a carboxyl, hydroxyl, epoxy, amino, melamine, fluro or acrylic group. These polymers are ideally suited for incorporation into grafting solutions; have sufficient graft segments so as to have a highly flexible graft polymer. The monomers can be an acrylate, methecrylate or urethane acrylate.

(73) Coatings provide protection according to mechanisms. The First mechanism is impermeability. The coating must be inert to chemical and impervious not only to air, oxygen, water and carbon dioxide, but also to the passage of ions and electrons. It also must have good adhesion. Such coating prevents abrasion by suppressing the process and chemical graft is superior to ordinary coating and gives chemical and abrasion resistance particularly in the healthcare environment.

(74) Acrylic and diacritic monomers having functional group such as carboxyl, hydroxyl, amino or ester are preferred. When a metallic salt such a silver nitrate, silver perchlorate, ferrous ammonium sulfate, silver acetate is utilized as graft initiator. Graft initiators are used in small quantities in order to ionize the metal salt to provide an activating metal ion, the graft solution includes a catalyst. A wide variety of catalysts may be utilized in the present invention. Peroxide of urea, hydrogen, and benzyl are used in most of the water based reactions. The catalyst functions to ionize metal salts into silver and iron or any other metal as graft initiator.

(75) This invention has particular application to furniture in hospitals and especially for chairs and beds. The coating described can be sprayed over the seat including under the seat and over the seams so as to make the seat seamless and sealed with a tough outer surface that is difficult to puncture, chemically resistant, and resistant to abrasion. Furthermore the under surface of the seats can include brackets or clips (that are also sprayed with the coating) that engage with the frame of the chair so that the seat can be easily removed or popped off for cleaning and the seamless aspect of the seat can be maintained.

(76) Furthermore chairs and beds in either hospital or hotel settings can have the outer surface or substrate made with the composition described so that the mattresses and seat cushions are sealed and seamless. This is highly desirable to combat bedbug infestations in hospitals and hotels as the treated surface will inhibit the infestation of these pests and prevent the spread of infection.

(77) The invention described herein can be used on a variety of other articles such as anti-fatigue mats, commodes, mattresses and wheelchair cushions.

(78) While it is apparent that the invention herein disclosed is well calculated to fulfill the objects above stated. It will be appreciated that numerous modifications and embodiments may be devised by those skilled in the art and it is intended that the appended claims cover such modification and embodiments as fall within the true spirit and scope of the present invention. It is within the scope of this invention to apply the grafting solution to polyurethane seating beds and other articles for abrasion, stain and chemical resistance, water proofing and other properties.