MXPA98006670A - Cement for pvc pipe based on m - Google Patents

Abstract

The present invention discloses a cement composition for PVC pipes containing a polymeric material of a homopolymer or copolymer of methyl methacrylate, a styrene-acrylonitrile polymer and a grafted rubber with at least one methacrylic acid ester of an alkanol of C1 to C8; and at least about 10% by weight of solvent. Cements for tubes of the invention form bonds or brazing and have a low volatile organic content compared to the materials currently used.

Description

CEMENT FARA PVC PIPE BASED ON MABS FIELD OF THE INVENTION The present invention relates to solvent-based cements for bonding pipe joints and polyvinyl chloride (PVC) fittings. This invention also relates to adhesives or sealants useful for joining or welding two polymeric surfaces, at least one of the * which is PVC. BACKGROUND OF THE INVENTION Almost half of the PVC manufactured today is used to form pipes, ducts and accessories. PVC pipes and fittings are widely used in the construction industry 15 in homes and businesses. For example, PVC pipes are used to transport drinking water and * water for domestic use; drain, discard and vent pipe (DMV); for outdoor plumbing as it can be for irrigation and sprinkler systems; for water tubs hot, spas and bath tubs, for electrical conduits. The cements or adhesives, which are used to form the joints of the PVC pipes, must comply with the norm of the joint strength of the overlapping cut and a standard of resistance to the hydrostatic burst, as established both in ASTM D 2564- 88, which is incorporated herein by reference. A strong bond between two pieces at least one of which is thermoplastic PVC, is obtained by softening the PVC with the solvent that is in the cement, so that the thermoplastic resin in the interphase of the pieces is joined in flow to join the pieces when they are pressed together. The PVC resin in the cement serves to cover any of the gaps between the pieces, thereby reinforcing the joint. The # Cements for conventional PVC pipes consist of: 10 from 10 or by weight up to about 14O by weight of the PVC resin in one or more organic solvents. In recent years, interest in the environment has given rise to efforts aimed at reducing volatile organic compounds (VOC) in industrial materials, 15 including cements for plastic pipes. Initial efforts usually include increasing the # resin content of the cement. It has been discovered, however, that when the amount of PVC increases from 10% by weight to more than about 14%. by weight, the cement 20 shows the consistency of a gel and is difficult to handle. In addition, to meet the specifications of ASTM D 2564-88, the cement must be capable of dissolving an additional 3% by weight of PVC resin without gelation. In larger amounts of about 14% by weight of PVC, however, the 25 common cement formulations show signs of gelation. Alternatively, the art provides compositions that include inert filler materials, for example, hollow ceramic spheres and thixotropic agents such as smoked silica and bentonite clay as described in Patel et al., U.S. Patent No. 5,252,634, and in Bush et al., US Patent No. 5,416,142, both patents are incorporated herein by reference. Cements contain a resin that is selected from chloride # 10 polyvinyl, chlorinated polyvinyl chloride and acrylonitrile-butadiene-styrene copolymer. The cements produced according to these patents are relatively expensive because of the cost of the hollow ceramic spheres. King, Mr., in the United States Patent No. 4,788,002, describes compositions containing 5 or 6 membered lactam rings with a co-solvent that is selected from # monoalcohols having up to 4 carbon atoms; lower alkyl esters (up to 4 carbon atoms) of lower alkanoic acids (also up to 4 carbon atoms) carbon); and PVC or ABS polymer. The co-solvents described by King, Sr. are volatile organic compounds that contribute to the VOC content of cement. It would be desirable to formulate a cement with a low VOC with a polymer that can contribute to the final bond strength of the adhesion or weld formed by the cement.

SUMMARY OF THE INVENTION It has now been discovered that a solvent-based cement, which contains a polymeric material of a rigid polymer of methyl methacrylate, a rigid polymer of styrene-acrylonitrile and a flexible copolymer of an alkyl methacrylate grafted on a rubber Unsaturated works exceptionally well in certain adhesion applications. In this way according to the present invention, a cement composition containing at least about 10 'is provided? by weight of a polymeric material of a rigid polymer methyl ethacrylate, a rigid polymer of styrene-acylonitrile and a flexible copolymer of an alkyl methacrylate grafted in an unsaturated rubber. The grafted rubber is preferably a copolymer of styrene-butadiene rubber (SBR) which is grafted with an alkyl methacrylate and, optionally, styrene. The cement composition of the invention also contains at least about 10% by weight of a solvent or a mixture of solvents. The cement may optionally contain other resins or thermoplastic polymers, such as polyvinyl chloride, chlorinated polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, acrylic, polycarbonate, cellulose acetate, polyacrylamide, polyamide or polystyrene. The invention also provides # A method of joining two pieces of plastic material, such as poly (vinyl chloride) tubing and fittings, and the produced part that has one or more joints formed by it. The cement compositions of the invention have reduced volatile organic content compared to cements for conventional PVC pipes, at functional viscosities. Moreover, the bonds formed with the cement of the present form strong bonds, useful for PVC pipes.

DETAILED DESCRIPTION The adhesive cements of the invention contain a polymeric material and one or more organic solvents. The polymeric material of the invention contains a methyl methacrylate polymer mainly, a styrene-acrylonitrile copolymer, an unsaturated rubber grafted with an alkyl methacrylate and, optionally, styrene. The 20 cements or adhesives of the invention also contain one or more solvents and, optionally, one or more additional resins. The preferred solvent is N-methylpyrrolidone or a mixture of solvents including an N-methylpyrrolidone. The polymeric material of the invention contains at least Less than about 15 parts by weight, preferably at least about 30 parts by weight of the polymer of mainly methyl methacrylate and contains up to about 70 parts by weight, preferably up to about 60 parts by weight, of the polymer of predominantly methyl methacrylate. In addition, the polymeric material of the invention contains at least about 10 parts by weight of the copolymer is tyro-acrylonitrile and contains up to about 50 parts by weight, preferably up to about 40 parts by weight of the styrene-acrylonitrile copolymer . The polymeric material of the invention also contains at least 20 parts by weight, preferably at least about 25 parts by weight unsaturated rubber grafted with alkyl methacrylate and contains up to about 50 parts by weight, preferably up to about 40 parts by weight of unsaturated rubber grafted with an alkyl methacrylate. Finally, the # polymeric material of the invention optionally contains styrene. (It will be appreciated that each of the above weight percent limitations, as well as each of The other quantitative limitations provided for the following invention may be employed alone or in combination with other limitations). The polymeric material preferably comprises a rigid component which is a homopolymer or copolymer of methacrylate of Methyl, a rigid polymer of styrene-acrylonitrile and a styrene-butadiene rubber cross-linked or grafted with methyl methacrylate. Such polymeric materials are commonly referred to as polymers of methacrylate acrylonitrile butadiene styrene (MABE). The preferred copolymer of the invention and its preparation is described in U.S. Patent No. 4,393,164 incorporated herein by reference. The rigid methyl methacrylate component can be a methyl methacrylate homopolymer or a copolymer of methyl methacrylate with at least about 0.5 weight of an alkyl acrylate having from 1 to 8 carbon atoms in the alkyl radical and up to about 10 percent, preferably up to about 7.0 percent, by weight of the alkyl acrylate having from 1 to 8 carbon atoms in the alkyl radical. Examples of # such acrylates include ethyl acrylate, propyl acrylate, and butyl acrylate. The rigid methyl methacrylate component preferably has a weight average molecular weight of at least about 60,000 and up to about 300,000 as measured by light deviation in chloroform. The styrene-acrylinitrile polymer component of the polymeric materials of the invention preferably is a copolymer of at least about 78 and up to about 88% by weight of styrene; and at least about 12 and up to about 22 weight acrylonitrile. The styrene-acrylonitrile polymer component preferably has a weight average molecular weight of at least about 5 60,000 and up to about 300,000, determined by light scattering in dimethylformamide. The grafted rubber component is formed from a rubber having a glass transition temperature of up to about -20 ° C. The grafted rubber can be * At least about 50 and can be up to about 80% by weight of a diene rubber, the difference in grafted rubber weight will be the grafted monomers. Preferably, the grafted monomers consist of at least about 40 or by weight and up to 100 or by weight of one or more methacrylic esters of alkanes from Ci to Ca, the difference being selected from styrene, alkyl styrenes having up to 12 carbon atoms and mixtures of these. In # a preferred embodiment, the rubber is a copolymer of a monomer that is selected from butadiene, isoprene and mixtures of these with styrene or a styrene with up to 12 carbon atoms, preferably a carbon atom substituted in the alpha position [hereinafter will be referred to as "alkylstyrene"]. Preferably, the rubber is the product of the reaction of at least about 60% and up to about 80% of butadiene, isoprene or mixtures thereof, the difference being styrene or alkyl styrene monomers. It is particularly preferred that the rubber be the product of the reaction of at least about 60 ° of butadiene and 5 to about 90 ° of butadiene, the difference being styrene. The rubber is grafted with one or more methacrylic acid esters of Ci to Ct alkanes and, optionally styrene or an alkyl styrene, having up to 12 carbon atoms. carbon. A small amount of acrylate monomer, such as methyl, ethyl, propyl or butyl acrylate, may be added to the monomer portion of the methacrylic ester. The rubber comprises at least about 50% by weight, preferably at least about 55% by weight 15 of graft polymer and up to about 80% by weight, preferably up to about 70% by weight of the graft polymer. . The weight difference of the graft polymer comes from the grafted monomers. The grafted monomers are used in a proportion of at least about 40 parts of the ester portion of methacrylic acid to about 60 parts by weight of the styrene or alkyl styrene monomers. The rubber can also be non-grafted. The grafted monomers can be reacted sequentially or as a mixture. The rubber can be produced by 5 5 by emulsion polymerization, in which case, after the introduction of the grafting process, the grafted rubber can be spray dried before preparing the polymeric material of the inventive compositions. The particle size of the grafted rubber should then be 0.2 microns or less. The polymeric materials or resins of the invention have at least about 15 parts by weight, preferably at least about 30 parts by weight of the methyl homopolymer or copolymer of methacrylate and up to about 70 parts by weight of preferably up to about 60 parts by weight of methyl methacrylate homopolymer or copolymer; at least about 10 '? by weight of the styrene-acrylonitrile polymer and up to about 50 parts by weight, preferably up to about 40 parts by weight of the styrene-acrylonitrile polymer; and at least about 20 parts by weight, preferably at least about 25 parts by weight of the grafted rubber, preferably rubber grafted styrene butadiene with methyl methacrylate, and up to about 50 parts by weight, preferably up to 20 about 40 parts by weight of grafted rubber, again preferably of styrene butadiene rubber grafted with methyl methacrylate. Customary additives can be added in amounts up to 20 i based on the weight of the resins. Examples of useful additives include copolymers / styrene maleic anhydride, colorants, stabilizers, lubricants and antistatic agents. The copolymer is prepared by mixing the homopolymer or methyl methacrylate copolymer, the styrene-acrylonitrile polymer and the graft polymer, together with some of the additives, in a molten state. The components are usually mixed at temperatures between 200 ° C and 300 ° C. The components can also be mixed together as solutions or suspensions, preferably in a suitable solvent for formulating the cement. It is particularly preferred that the copolymer be a methyl methacrylate-acrylonitrile-butadiene-styrene (MABS) material. MABS materials are available commercially, for example, under the trade name Terlux © from BASF Corp., Mount Olive, NJ. 15 Because MABS polymeric material is more soluble in solvents that are commonly used in cements for PVC pipes, the concentration of the # Copolymer in the cement may be higher than the concentration of PVC in conventional cements. The MABS material is preferably included in a concentration of at least 10o by weight, more preferably at least about 20o by weight. Also preferably, the MABS material is up to about 60% by weight of the cements of the present invention, most preferably up to about 40% by weight of the cement.

A large number of solvents or solvent mixtures may be useful in the cements, sealants and adhesives of the invention. The solvent or solvent mixture that is chosen must be liquid, volatile and capable of solvating or dispersing the components of the cement, sealant adhesive. The solvent or solvent mixture also participates conveniently in the adhesion process by solvating or softening the thermoplastic materials to be joined. In this way, the choice of specific solvents 10 will depend on the nature of the materials to be joined. The types and quantities of solvents that are preferably used are chosen so that the cement compositions meet or exceed the standards for bond strength established by ASTM D 2564-88"standard specification for solvent-based cements for tubes. and poly (vinyl chloride) (PVC) plastic accessories, which is incorporated herein by reference. • Examples of useful preferred solvents include lower alcohols such as methanol, ethanol, isopropanol; ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl isoamyl ketone, isophorone and cyclohexanone; esters such as methyl acetate, ethyl acetate, ethyl formate, ethyl propionate, butyl acetate, propyl propionate, gamma-butyrolactone and epsilon-caprolactone; halogenated solvents such as dichloromethane, dichloroethane, carbon tetrachloride, chloroform, trichloroethane and dimethylformamide; ethers such as propylene glycol monomethyl ether and dioxane; other liquids such as tetrahydrofuran and N-methylpyrrolidone; and 5 mixtures of these. When the materials to be joined will be in contact with drinking water, it is preferred to use solvents for which the maximum permissible levels have been established by the National Sanitation Foundation (NSF) for use in potable water pipe. These solvents herein are methylethyl ketone, tetrahydrofuran, cyclohexanone, dimentylformamide, acetone and N-methylpyrrolidone. The MABS polymer has excellent solubility in solvents approved by the NSF for drinking water pipe systems. It is especially advantageous to use up to 50% by weight of N-methylpyrrolidone in the cement compositions. The N-methylpyrrolidone has a low vapor pressure, which results in good storage characteristics. The solvents of More rapid evaporation such as methylethyl ketone, tretrahydrofuran and acetone tend to evaporate from the cement over time, giving rise to an increased viscosity. In addition, N-methylpyrrolidone is an excellent solvent for PVC and has low toxicity. The compositions of the invention contain at least about 10 by weight, preferably at least about 500 by weight and particularly preferably at least about 50o by weight of the solvent or a mixture of solvent. The compositions of the invention also contain up to about 90% by weight, preferably up to about 80% by weight of the solvent or a combination of solvents. In a preferred embodiment, at least about 10o by weight and up to about 50 '? by weight of N-methylpyrrolidone is used in the preparation of a cement. It is preferred to use no more than 50o by weight of N-methylpyrrolidone because the slow evaporation of the N-methylpyrrolidone would mean that the bonds formed with the compositions containing more than about 50o by weight of N-methylpyrrolidone would take longer to develop the 15 final properties as resistance of the overlap cut. To develop the resistance of the overlap cut and the # resistance to the hydrostatic burst more quickly, the cement may include a faster evaporating solvent such as methyl ethyl ketone, which volatilizes rapidly to allow the cement to harden (cure). When other solvents are used instead or in addition to N-methylpyrrolidone, is it preferred that the solvents be at least about 35 weight percent, and most preferably up to about 80 '? by weight of methyl ethyl ketone, preferably at least about 2o by weight and preferably up to about 50 or by weight of tetrahydrofuran; at least about 2o by weight is preferred and up to about 10O by weight of cyclohexanone is preferred; preferably at least about 2 or by weight and up to about 10 or 5 weight of dimethylformamide; or preferably at least about 2? by weight and up to about 50% by weight of acetone. Cement, sealant or pipe adhesive can be prepared by any means. Although the polymeric materials can be first dissolved in the solvent or the mixture of solvents, followed by the addition of any of the other materials or additives, other methods of preparation are contemplated within the scope of the invention. 15 Pipe cements including pipe cements of the present invention are usually formulated to have one of the three normal viscosities used in the industry. In accordance with ASTM D 2564-88 guidelines, a cement of consistency regular has a minimum viscosity of about 90 centipoise (cP); a cement of medium consistency has a minimum viscosity of about 500 cP; and a cement of dense consistency has a minimum viscosity of about 1600 cP. All viscosities are measured around 23 ° C.

In general, denser viscosity cement grades are used for pipes that have larger diameters or for fittings without interference. ASTM D 2564-88 specifies that the minimum viscosity to be used in 8 to 12 inch tubes is 1600 cP and the minimum viscosity that should be used from 2.5 to 6 inches is 500 cP for adjustments with interference and 1600 cP for adjustments without interference. Higher viscosity cements form thicker films and deposit more resin in the empty spaces. It will be appreciated that the cement, sealant and adhesive compositions of the invention may contain optional ingredients, including those well known in the art, such as fillers, pigments, dyes, colorants, viscosity modifying agents, stabilizers and others. . These materials are commercially available and the concentrations and methods of incorporation are well known to those skilled in the art. Examples of useful additives include thermal stabilizers such as organometallic compounds including tin and dialkyl tin compounds; plasticizers such as phthalate esters; pigments; other colorants, fillers and viscosity modifying agents such as colloidal silica; amorphous silica, silica flour, crushed quartz, carbon black, dioxide titanium, barium sulfate, iron oxide, talc, wands,? smoked silica, treated bentonite, clays, calcium carbonate, magnesium silicate, magnesium oxide, micas and hollow silica-alumina alloys, ceramic materials such as Zeelan Z-Ligth spheres. 5 Tube cements are usually applied by a process that includes the application of an initiator or primer followed within five minutes, preferably within about 1 minute, and particularly preferably about 30 seconds to about 1 minute. minute by application of cement. The first is used to help soften one or both pieces that are to be joined. Usually the first is a mixture of the same solvents found in cement. The primer also commonly includes one or more pigments or dyes. The pigments or dyes can be included so that a building inspector can observe that the first was used when making the joint. The cement is applied by brush on one, or preferably both surfaces of the joint and then put in contact the two pieces that are going to be joined. The cement, like the first or initiator, softens the contact surfaces of the joined pieces. The cement can be applied in one or more coatings. The pieces to be joined are brought into contact while the plastic 25 is still in a softened state. Usually, the pieces are joined immediately after the final layer of cement or at least within about 1 minute, and preferably within about 30 seconds. Although the parts must be, and preferably are machined for an airtight fit, some gaps will still remain. The purpose of the resin in cement is to fill the gaps to form a strong and durable bond between the joined pieces. In this way, enough cement must be applied to fill any gap between the joined pieces. 10 When joining PVC pipes and fittings, the preferred procedure is ASTM D 2855-90, "normal practice for bonding with solvent-based cement with poly (vinyl chloride) pipe and fittings (PVC) ) ", which is incorporated in the present as reference. The assembled joint is allowed to harden for the time recommended by the ASTM method before installation. The assembled joint is allowed to harden completely (cure) before putting it into use. During installation and hardening, the solvent evaporates and thermoplastic materials harden. The times needed to install and harden depend on the environmental conditions and are in accordance with the experience of the person with ordinary skill in the art. The fixation or hardening of the joint results from the evaporation of solvents. The solvated resins of the surfaces and the resin in the cement are dried through the evaporation of the solvent and forms a continuous and hermetic joint. The invention is illustrated by the following example, the example is merely illustrative and does not in any way limit the scope of the invention as described and claimed. All parts and percentages are by weight unless otherwise stated. * 10 Examples Example 1. Cement with a content of 25 weight percent MABS. The cement was prepared by mixing: Methyl ethyl ketone 52.5 'by weight 15 N-methylpyrrolidone 15'? by weight Tetrahydrofuran 3.75 '? in weight so i The MABS used was Terlux 2808, available at 20 from BASF Corp., Mount Olive, NJ. The properties and performance of the cement of example 1 were tested according to the following tests and with the following results: (1) Hydrostatic burst strength, test method ASTM D 2564-88: minimum acceptable hydrostatic burst strength 400 psi in a hardening time of 2 hours. The hydrostatic burst strength of Example 1 was measured as 940 psi at the hardening time of 17 hours. (2) Overlap cut resistance, ASTM D 2564-88 test method: the overlap cut resistance was measured as 424.4 psi at the hardening time of 48 hours. (3) VOC content according to South Coast Air Quality VOC of Example 1 was measured as 350 g / 1. (4) Viscosity of Example 1: 100 cP. The invention has been described in detail in relation to the preferred embodiments thereof. It should be understood, however, that variations and modifications may be made within the spirit and scope of the invention and the appended claims.

Claims (5)

CLAIMS #

1. A cement composition for PVC pipe consisting of: (a) at least about 10% by weight of a polymer material of a methyl methacrylate homopolymer or copolymer, a styrene-acrylonitrile polymer and a rubber grafted with at least one methacrylic acid ester of an alkanol from Ci to Cb; 10 and (b) at least about 10O by weight of organic solvent.

2. The cement composition according to claim 1 contains at least one solvent which is selected from the group consisting of methylethyl ketone, tetrahydrofuran, cyclohexanone, dimethylformamide, acetone, N-methyl pyrrolidone and mixtures thereof.

3. The cement composition according to claim 1, wherein the solvent consists of N-methyl pyrrolidone.

4. The cement composition according to claim 1, wherein the solvent contains up to 50o by weight of N-methyl pyrrolidone.

5. The cement composition according to claim 1, wherein the rubber is a copolymer of a monomer selected from the group consisting of butadiene, isoprene and mixtures thereof, with styrene or alkyl styrene, having the alkyl group up to 12 carbon atoms. . The cement composition according to claim 1, wherein the rubber is a reaction product of about 60 to about 90% of a monomer selected from the group consisting of butadiene, isoprene and mixtures thereof, with from about 10 to about 40% styrene or alkyl styrene, the alkyl group having up to 12 carbon atoms. The cement composition according to claim 1, wherein the rubber is a styrene-butadiene rubber. 8. The cement composition according to claim 1, wherein the rubber is a styrene-butadiene rubber and further wherein the rubber is grafted with at least methyl methacrylate. 9. The cement composition according to claim 1, wherein the polymeric material consists of: (a) from about 15 to about 70 parts by weight of methyl methacrylate polymer having from about 90 to 100 percent by weight of methyl methacrylate and the difference being an alkyl acrylate having from 1 to 8 carbons in the alkyl radical; (b) from about 10 to about 50 parts by weight of styrene-acrylonitrile copolymer having from 5 about 78 to 88 weight percent of styrene and the difference being acrylonitrile; and (c) from about 20 to about 50 parts by weight of a grafted rubber that is from about 50 to about 80? of a diene rubber and the difference being 10 grafted monomers, wherein the grafted monomers consist of from about 40 to 100O by weight of one or more methacrylic esters of albandes from Ci to CB and the selected difference being from styrene, alkyl styrenes that have up to 12 atoms 15 carbon and mixtures of these. A method for joining two surfaces of thermoplastic material together in a joint or solder, comprising the steps of: (a) applying a cement composition according to claim 1 to at least one of the surfaces that are to be removed. to join; (b) allow the surface or surfaces to be softened by the cement; (c) joining the two surfaces together while the surface 25 is still in a softened state; and (d) allow the joint or weld to fully harden. 11. A method for joining two surfaces of thermoplastic material together in a joint or solder, comprising the steps of: (a) applying a cement composition according to claim 9 to at least one of the surfaces that are to be removed. to join; (b) allowing the surface or surfaces to soften by cement; (c) joining the two surfaces together while the surface is still in a softened state; and (d) allow the joint or solder to harden completely. 12. An article having at least one joint or weld formed according to the method of claim 10. * 13. An article having at least one joint or weld formed in accordance with the method of the claim. 20 11.