WO2000050494A1

WO2000050494A1 - Low voc (volatile organic compounds), dimethyl-2-piperidone solvent-based, pvc and cpvc pipe and component adhesives and primers containing minimal or no tetrahydrofuran

Info

Publication number: WO2000050494A1
Application number: PCT/US2000/004509
Authority: WO
Inventors: Naresh D. Patel; Edward D. Otremba; Rashid H. Siddiqi
Original assignee: Ips Corporation
Priority date: 1999-02-23
Filing date: 2000-02-23
Publication date: 2000-08-31
Also published as: AU3499400A; US6372821B1

Abstract

Novel low VOC solvent-based adhesives are provided, comprising a mixture of low vapor pressure, isomeric dimethyl-2-piperidones (DMPD) blended with (1) a non-solvent diluent, specifically, acetone (a VOC-exempt compound), or with mixtures of acetone and other known ketonic solvents such as methyl ethyl ketone (MEK), diethyl ketone (DEK), methyl propyl ketone (MPK), and methyl iso-butyl ketone (MIBK), cyclohexanone, and (2) thermoplastic PVC or CPVC resins. Omission of the resin provides a novel primer for pipes. The blended mixtures yields PVC or CPVC pipe adhesives and primers that: (1) result in low VOC formulas (e.g., less than 510 g/l for PVC pipe and less than 490 g/l for CPVC pipe); (2) are very economical in the industry; (3) yield strong, quick setting, durable pipe joints that meet the required standards and performance criteria (e.g., ASTM D-2564 lap shear for PVC); (4) yield stable, low viscosity solutions that, in the case of adhesives, can be readily adjusted with thixotropes (e.g., Aerosil 200) to give desirable flow characteristics and body, as well as primers for sovlent welding PVC and CPVC pipe and components; and (5) can be formulated with minimal (10 wt.%) or no cyclic ethers such as THF.

Description

LOW NOC (VOLATILE ORGANIC COMPOUNDS), DIMETHYL- 2-PIPERIDONE SOLVENT-BASED, PVC AND CPVC PIPE AND COMPONENT ADHESIVES AND PRIMERS CONTAINING MINIMAL OR NO TETRAHYDROFURAN

TECHNICAL FIELD The present invention relates generally to thermoplastic pipe adhesive and pnmer com- positions, and, more particularly, to adhesives and pπmers used for joining PCV (polyvinyl chloπde) and CPVC (chloπnated PVC) pipe. Specifically, the PVC and CPVC pipe adhesives and pπmers disclosed and claimed herein are solvent-based, having an environmentally- acceptable VOC (volatile organic compounds) content.

BACKGROUND ART

Solvent-based adhesives, or cements, have been in use for joining thermoplastic pipe for over 30 years. The development of these adhesives is largely responsible for growth of the thermoplastic pipe industry. Several billion pounds of plastic pipe are produced each year in North Amenca. Rapid-settmg, solvent-based adhesives weld the pipes together m a timely manner. These rapid-setting adhesives allow for the tesfang and trouble-shootmg of piping systems in a matter of hours while maintaining the long-term durability of the pipe itself These characteπsfacs, rapid set, ease of use, long-term durability along with low-cost, have made the joining of plastic pipe by solvent-based adhesives a practical and economic system

The solvent-based adhesives work pπmaπly by two means of action First, the solvent portion of the formulation softens the outer surfaces of the pipe through solvation of the plastic

Subsequently, the adhesive joint "cures" (hardens) by means of the solvents evaporating to the surrounding atmosphere from the pipe. Secondly, the resm dissolved m the adhesive dπes through solvent evaporation and provides continuity between the welded pipe surfaces which aid in preserving the mtegπty of the entire pipe system. These adhesives cure rapidly (within a matter of hours), often allowing piping systems to be tested the same day as constructed. However, perhaps the most important benefit of these solvent-based adhesives is the maintenance of the integnty of the pipe itself. The resm is the same as the plastic pipe and/or fitting mateπal. This provides a high degree of long-term dura- bihty for the piping system, often up to 30 to 40 years of useful life. This is essential for these systems which are built into the structures of homes and buildings, or are buπed underground

Thousands of miles of thermoplastic piping systems are constructed each day throughout the world, pπmaπly by the means previously descπbed. These systems are used in the transfer of potable water for dπnking; residential hot and cold water systems; dram, waste, and vent (DWV) applications in home and industry; turf and agπcultural spπnkler systems, jacuzzi, spa and tub connections, residential and commercial fire spπnkler systems; etc. These systems are crucial to the maintenance of safe and healthy means of transport of water and other chemicals throughout the world.

Evaporation of solvents from adhesives is a concern to an environmentally-concerned world, along with all other potential sources of air pollution. Typical solids (non- volatile) contents of plastic pipe adhesives are 10 to 20% for both PVC and CPVC. The balance of the formulation is solvent. By definition, the solvents normally used, e.g., tetrahydrofuran (THF), methyl ethyl ketone (MEK), and acetone are considered to be VOCs. That is, they are volatile compounds which contain the element carbon excluding methane, carbon monoxide, carbon di- oxide, carbonic acid, metallic carbides and carbonates, ammonium carbonate, and exempt compounds, such as methylene chloπde and 1,1,1-tnchlorethane. While other solvents, such as cyclohexanone and dimethyl formamide (m the case of PVC) and cyclohexanone (m the case of CPVC), may also be used in such adhesives, the amount of such solvents are typically minor, considerably less than 15 wt% (in the case of PVC) and 10 wt% (in the case of CPVC) of the total adhesive concentration. Typical VOC values of present commercial PVC solvent adhesives range from 750 to 850 grams/liter and for CPVC solvent adhesives range from 775 to 850 g/1-

Regulations are being created throughout North Ameπca regarding allowable VOC levels in adhesive formulations. Federal, state, and local agencies are beginning to adopt stπct measures to drastically reduce these levels. The South Coast Air Quality Management Distπct

(SCAQMD) m the Los Angeles area has been a leader of the establishment of rules governing VOCs, such as SCAQMD Rule 1168. SCAQMD Rule 1168 specifies a VOC level for PVC adhesives of 510 g/1 or less and for CPVC adhesives of 490 g/1 or less, as determined by Method 316-A. All PVC and CPVC adhesives used after January 24, 1994, are required to meet that maximum allowed level.

More recently, acetone has been removed from the list of solvents and placed on the list of exempt solvents. Consequently, there is, at the present fame, no legal limit to the amount of acetone that can be added to adhesive compositions.

Further, tetrahydrofuran (THF), which has been a major component of PVC and CPVC adhesive compositions (typically, 25 to 75 wt%), has been found by the National Toxicology Board to have a slight carcinogenicity m animal testing. As a result, THF is under extensive m- vesfagation, both with regard to worker health (exposure duπng pipe assembly) and potable water issues. Furthermore, THF is a high vapor pressure, fast-evaporatmg solvent that heavily contπbutes to the VOC level. It is highly desirable to reduce THF levels, but still maintain the adhesive-contπbufang properties that THF offers, i.e., fast-setting, durable pipe joints.

Also, many PVC and CPVC pipe adhesives are formulated with N-methyl pyrrohdone (NMP), a very effective solvent for PVC and CPVC resms. However, the hygroscopicity of this solvent results m milky white cured film joints, even in pigmented blue and gray formulas, and this is undesirable m many applications.

Other thermoplastic pipe adhesives are formulated with large amounts of low vapor pressure solvents blends, such as di-methyladipate (available from E. I. DuPont de Nemours as DBE-6) and NMP and/or alkyl-substituted naphthalene (U.S. Patent 5,821,289, issued to CD. Congeho et al) to reduce VOC levels, but generally these type of adhesives require longer set fames before water pressure testing of the system can be made. Also, these slower setting adhesives are less effective in colder environments.

Still another method to formulate low VOC cements for thermoplastic pipe and other PVC and CPVC extruded articles is to incorporate higher amounts of resm(s). This does indeed reduces VOC levels, but is less cost effective and generally slower than cements containing lower weight percent of resm.

Thus, adhesives for joining PVC and CPVC pipes having a maximum VOC level of 510 g/1 (for PVC) or 490 g/1 (for CPVC) are required. Yet, such adhesive must also meet the required hydrostatic burst strength and other performance cπteπa set forth in ASTM F-493 and

D-2846 and lap shear strength set forth in ASTM D-2564. (Test method 316A has been revised and the new acceptable VOC levels are shown above.) DISCLOSURE OF INVENTION In accordance with the present invention, novel low VOC solvent-based adhesives are provided, compnsmg a mixture of low vapor pressure isomeπc dιmethyl-2-pιpeπdones (DMPD) blended with (1) a non-solvent diluent, specifically, acetone (a VOC-exempt compound), or with mixtures of acetone and other known ketomc solvents such as methyl ethyl ketone (MEK), diethyl ketone (DEK), methyl propyl ketone (MPK), and methyl iso-butyl ketone (MIBK), cyclohexanone, and (2) thermoplastic PVC or CPVC resms. Pπmers are also provided in accordance with the present invention by omitting the inclusion of the thermoplastic resm o The novel adhesives descπbed herein overcome the deficiencies descπbed above for the prior art adhesives without compromising adhesive performance. The adhesives of the present invention comprise:

(a) 5 to 95 wt% of low vapor pressure lsomeπc dιmethyl-2 pipeπdones (DMPD; a DuPont product containing 64 to 71 wt% of 1,3-dιmethyl pipeπdone and 29 to 36 5 wt% of 1 ,5-dιmethyl pipeπdone);

(b) 15 to 75 wt% of at least one ketone selected from the group consisting of acetone (which is a non-solvent for PVC and CPVC and a VOC-exempt compound), and MEK (methyl ethyl ketone), cyclohexanone, DEK (diethyl ketone), MPK (methyl propyl ketone), MIBK (methyl iso-butyl ketone), MAK (methyl amyl ketone), etc. (which are sol- 0 vents for PVC and CPVC);

(c) from 0 to 30 wt% thermoplastic resms such as PVC (e.g., Shmtech SE- 650) or 0 to 30 wt% CPVC resin (e.g., BF Goodπch Tempπte 677x670 with 67% chloπna- tion); and, optionally,

(d) blends of resin such as 5 to 25 wt% PVC and 2 to 25 wt% of acrylic 5 (homo-, co-, or ter-polymers) resin such that the PVC and acrylic resm range from 12 to 35 wt% of adhesive.

Inclusion of the resm component provides pipe adhesives, while omission of the resm component provides pipe pπmers.

DMPD, which is used in the novel adhesive of the present invention, is a true solvent 0 for PVC and CPVC and exhibits a remarkable decrease in solution viscosity when blended with the non-solvent acetone or the other ketones (MEK, DEK, MPK, cyclohexanone, MIBK, MAK, etc.), thereby allowing great latitude in formulation. Blends of DMPD can be adjusted for such parameters as set fame, VOC content, cost, viscosity, flash point, solids content very readily with little effect on adhesive performance. The adhesive in this invention may include filler, thixotropic agents, colorants, stabilizers, ohgomeπc and polymeπc rheology additives, wetting agents and adhesion promoters.

The blended mixture yields PVC or CPVC pipe adhesives that: (1) result in low VOC formulas (e.g., less than 510 g/1 for PVC pipe and less than

(2) are very economical m the industry;

(3) yield strong, quick setting, durable pipe joints that meet the required standards and performance criteria (e.g , ASTM D-2564 lap shear for PVC); (4) yield stable, low viscosity solutions that can be readily adjusted with thixotropes

(e.g., Aerosil 200) to give medium and high body adhesives, as well as low bodied adhesives and pπmers for solvent welding PVC and CPVC pipe and components, and

(5) can be formulated with minimal (10 wt % maximum) or no cyclic ethers such as THF. Other objects, features, and advantages of the present invention will become apparent upon consideration of the following detailed descπpfaon

BEST MODES FOR CARRYING OUT THE INVENTION Reference is now made in detail to a specific embodiment of the present invention, which illustrates the best mode presently contemplated by the inventors for practicing the invention. Alternative embodiments are also bπefly descπbed as applicable.

In accordance with the present invention, novel low VOC solvent-based adhesives are provided, compπsing a mixture of low vapor pressure isomeπc dιmethyl-2-pιpeπdones (DMPD) blended with (1) (a) a non-solvent diluent, specifically, acetone (a VOC-exempt com- pound), or (b) with mixtures of acetone and other known ketonic solvents such as methyl ethyl ketone (MEK), diethyl ketone (DEK), methyl propyl ketone (MPK), methyl iso-butyl ketone (MIBK), methyl amyl ketone (MAK), and cyclohexanone, or (c) with one or more of the foregoing ketonic solvents without acetone, and (2) thermoplastic PVC or CPVC resins

The novel adhesives described herein overcome the deficiencies described above for the prior art adhesives without compromising adhesive performance. The adhesives of the present invention compπse-

(a) 5 to 95 wt% of low vapor pressure lsomeπc dιmethyl-2 pipeπdones (DMPD; a DuPont product containing 64 to 71 wt% of lJ-dimethyl pipeπdone and 29 to 36 wt. % of 1,5-dιmethyl pipeπdone); (b) 15 to 75 wt% of at least one ketone selected from the group consisting of acetone, methyl ethyl ketone, cyclohexanone, diethyl ketone, methyl propyl ketone, methyl iso-butyl ketone, methyl amyl ketone, acetophenone, methyl iso-propyl ketone, methyl butyl ketone, methyl iso-amyl ketone, di-butyl ketone, and ethyl amyl ketone; (c) from 0 to 30 wt% thermoplastic resins such as PVC (e.g., Shintech SE-

650) or 0 to 30 wt% CPVC resin (e.g., BF Goodrich Temprite 677x670 with 67% chlorina- tion); and, optionally,

(d) blends of resin such as 5 to 25 wt% PVC and 2 to 25 wt% of acrylic (homo-, co-, or ter-polymers) resin such that the PVC and acrylic resin range from 12 to 35 wt% of adhesive .

Inclusion of the resin component provides pipe adhesives, while omission of the resin component provides pipe primers.

DMPD, which is used in the novel adhesive of the present invention, is a true solvent for PVC and CPVC and exhibits a remarkable decrease in solution viscosity when blended with the non-solvent acetone or the other ketones (MEK, DEK, MPK, cyclohexanone, MIBK, MAK, etc.), thereby allowing great latitude in formulation. Blends of DMPD can be adjusted for such parameters as set time, VOC content, cost, viscosity, flash point, solids content very readily with little effect on adhesive performance.

Acetone may be employed as the sole ketone in the range of about 15 to 75 wt% of the total adhesive or primer composition. Alternatively, a mixture of acetone and at least one of the other above-enumerated ketones may be employed, the total concentration falling within the same range. Finally, at least one of the above-enumerated ketones, other than acetone, may be used in the practice of the present invention.

In particular, the ketone component may comprise 15 to 75 wt% of at least one ke- tone selected from the group consisting of 15 to 75 wt% (1) acetone; (2) a low boiling ketone having a boiling point less than 80°C, such as MEK; (3) a medium boiling ketone having a boiling point within a range of about 80° to 130°C, such as DEK and MPK; and (4) a high boiling ketone having a boiling point greater than 130°C, such as cyclohexanone, wherein the medium boiling ketone and the high boiling ketone have a maximum amount of 35 wt%. With regard to the PVC resin, its incorporation into the adhesive composition provides an adhesive for PVC pipe. In addition, acrylic resins may be included, as disclosed in U.S. Patent 5,422,388, issued to Naresh D. Patel et al on June 6, 1995. The concentration of PVC resin is in the range of about 5 to 25 wt% of the total adhesive composition. The acrylic resin, if employed, is in the range of about 2 to 25 wt%, with the concentration of both PVC and acrylic resin ranging from about 12 to 35 wt% of the adhesive composition (A minimum of 10 wt% resin is permitted under ASTM-2564.) A concentration of PVC beyond the maximum value of 25 wt% would not be shelf-stable. With regard to the acrylic resin, less than about 2 wt% does not result m the benefits provided to the adhesive by its presence m combination with the PVC resm, while greater than about 25 wt% is not soluble in the solvent system.

Withm the foregoing constraints, the total resm level in the adhesive ranges from about 12 to 35 wt%, as indicated above. Less than about 12 wt% makes it difficult to achieve VOC levels (if formulated without acetone or significant levels of DMPD) less than the per- mitted maximum of 510 g/1, while greater than about 35 wt% is not shelf-stable

Any of the PVC resms commonly employed in PVC adhesives may be used in the practice of the present invention. Particularly preferred are those PVC resms characterized by homopolymers as classified by inherent viscosity (IN.) in the range of about 0.6 to 0.95 The inherent viscosity of a PVC resm is determined m accordance with ASTM D-1243. Inherent viscosity is a qualitative measure of molecular weight; that is, the higher the I V., the higher the molecular weight.

The acrylic resins advantageously employed in the practice of the present invention are those homopolymers, copolymers, and terpolymers of methyl methacrylate. When char- acteπzed by inherent viscosity, as measured with a solution containing 0J5 g polymer m 50 ml methylene chloπde at 20°C using a No. 50 Cannon-Fenske Viscometer, the useful range in the practice of the present invention is 0J to 1.25. Alternatively, an acrylic resm having a melt flow rate as determined by ASTM D-1238 in the range of 1.6 to 24 is acceptable Examples of acrylic resms suitably employed in the practice of the present invention include (1) the V series (VS, VM, VH) resins from Atohaas, (2) the Elvacite® and Lucite® acrylic res- s, both available from ICI, and (3) Acnterm® HS resms from ICI.

With regard to the CPVC resm, its incorporation into the adhesive composition provides an adhesive for CPVC pipe. As indicated above, the CPVC resm is contained in the adhesive formulation in an amount ranging from about 5 to about 25 wt%, preferably from about 5 to about 15 wt% of the total adhesive. If too small an amount of CPVC resm is used, it may not be possible to form an effective and durable pipe joint and VOC levels will tend to increase, while, if the amount of CPVC resm too great, it may not all solubihze in the solvents) and thus tends to form an undesirable "gel" therewith.

CPVC resms useful in this invention may be prepared by chloπnation of polyvinyl chloride homopolymers and copolymers starting materials by procedures known to those skilled m the art. Examples of useful polyvinyl chloπde homopolymers and copolymers starting mateπals in this regard include those described in U.S. Pat. No. 5,384,345, which teachings are incorporated herein by reference. CPVC resms are typically supplied m powder form when obtained from commercial sources. The CPVC resms used in this invention may contain chloπne in any amount effective to impart adequate heat deflection resistance property to the adhesive composition for the intended use(s). The chloπne content of the CPVC resms used in the compositions of this invention will range from about 50 to about 80% by weight, and more specifically about 57 to about 70% by weight

Particularly preferred are those CPVC resins characterized by an inherent viscosity (IN-) ranging from about 0.60 to 0.95, and more preferably about 0.68 to about 0.92

The adhesives of the present invention may include additional solids. Such additional solids that may be present include fillers, thixotropic agents, colorants, stabilizers, oligomeπc and polymeric rheology additives, wetting agents, and adhesion promoters. Up to about 8 wt% of the adhesive may contain such additional additives and adjuvants Any fillers, thixo- tropic agents, pigments, dyes, stabilizers oligomeπc and polymeric rheology additives, wetting agents, and adhesion promoters that are commonly used m PVC and CPVC adhesives may be employed in the practice of the present invention.

Preferred fillers low specific gravity hollow spheres (glass, ceramic, or synthetic, e.g., PVC), and include solid particulate inorganic fillers such as calcium carbonate, alumi- num tπhydrate, calcium sulfate, and crystalline silica.

Preferred colorants include dyes and pigments, such as titanium dioxide, carbon black, aluminum Lake based-orange, and conventional red or yellow colorants

Preferred thixotropic agents include fumed silica and precipitated silica (e g , AEROSIL-200 available from Degussa Corporation, Cab-O-Sil MS available from Cabot Corporation, and HISIL T600) and treated bentonite clay (e.g., Bentone 27), and these may be used at low levels to obtain optimum flow properties, especially with regard to controlling spillage from the pipe upon application.

Preferred stabilizers include such additives as acid scavengers, antioxidants (e.g , hindered phenols) and tin stabilizers. Preferred rheology additives include non-PVC or non-CPVC thermoplastic resms, such as one or more of thermoplastic PVC polymers (in the case of CPVC adhesives), acrylic polymers (in the case of CPVC adhesives), MBS polymers, ABS polymers, linear and core/shell polymers, and random and block polymers including elastomeπc and rubber res The blended mixture yields PVC or CPVC pipe adhesives that:

(1) result in low VOC formulas (e.g., less than 510 g/1 for PVC pipe and less than 490 g/1 for CPVC pipe);

(2) are very economical in the industry; (3) yield strong, quick setting, durable pipe joints that meet the required standards and performance cπteπa (e.g., ASTM D-2564 lap shear for PVC);

(4) yield stable, low viscosity solutions that can be readily adjusted with thixotropes (e.g., Aerosil 200) to give desirable flow characteπstics and body to adhesives, as well as primers for solvent welding PVC and CPVC pipe and components; and (5) can be formulated with minimal (10 wt% maximum) or no (0 wt%) cyclic ethers such as THF.

A number of different, specific composition ranges are preferred. These include

(a) about 5 to 25 wt% PVC resm; about 5 to 50 wt% DMPD; and about 15 to 68 wt% acetone.

(b) about 5 to 25 wt% PVC resm; about 5 to 50 wt% DMPD; about 15 to 68 wt% acetone; and up to about 10 wt% tetrahydrofuran (c) about 5 to 25 wt% PVC resm; about 5 to 50 wt% DMPD; about 15 to 68 wt% acetone; and up to about 50 wt% MEK, where acetone and MEK together total about 15 to 68 wt% of the adhesive. (d) about 5 to 25 wt% PVC resm; about 5 to 50 wt% DMPD; about 15 to 68 wt% acetone; and up to about 35 wt% cyclohexanone, where acetone and cyclohexanone together total about 15 to 68 wt% of the adhesive. (e) about 5 to 25 wt% PVC resm; about 5 to 50 wt% DMPD; about 15 to 68 wt% acetone; and up to about 35 wt% of at least one of MPK and DEK, where acetone, MPK, and DEK together total about 15 to 68 wt% of the adhesive. (f) about 5 to 25 wt% PVC resin; about 5 to 50 wt% DMPD; about 15 to 68 wt% acetone; and up to about 35% of at least one of cyclohexanone, MPK, and DEK, where acetone, MPK, DEK, and cyclohexanone together total about 15 to 68 wt% of the adhesive.

(g) about 5 to 25 wt% PVC resin or CPVC resin; about 5 to 50 wt% DMPD; and about 15 to 68 wt% methyl ethyl ketone. (h) about 5 to 25 wt% PVC resin or CPVC resin; about 5 to 50 wt% DMPD; about 15 to 68 wt% methyl ethyl ketone; and up to about 10 wt% THF. (i) about 5 to 25 wt% PVC resin or CPVC resin; about 5 to 50 wt% DMPD; about 15 to 68 wt% methyl ethyl ketone; and up to about 35 wt% cyclohexanone, wherein methyl ethyl ketone and cyclohexanone together total about 15 to 68 wt% of the adhesive.

(j) about 5 to 25 wt% PVC resin or CPVC resin; about 5 to 50 wt% DMPD; about 15 to 68 wt% methyl ethyl ketone; and up to about 35 wt% of at least one of MPK and DEK, wherein methyl ethyl ketone, MPK, and DEK together total about 15 to 68 wt% of the adhesive, (k) about 5 to 25 wt% PVC resin or CPVC resin; about 5 to 50 wt% DMPD; about 15 to 68 wt% methyl ethyl ketone; and up to about 35 wt% cyclohexanone, wherein methyl ethyl ketone, MPK, DEK, and cyclohexanone together total about 15 to 68 wt% of the adhesive.

The formulations provided above, if the solids (PVC or CPVC resin and solid additives) are omitted, are primers, and may be used as such with both PVC and CPVC pipes. Primers may be employed as part of a two-step process, comprising applying the primer to one or both surfaces of the pipes (or other objects) being joined, followed by applying the adhesive. EXAMPLES

Examples 1-6: Comparative Examples 1J.

The compositions listed in Table I below exemplify some typical preferred composi- faons with low VOC values. SCAQMD Rule 1168 specifies a VOC level for PVC adhesives of 510 g/1 or less. In Examples 1-3, DMPD and MEK adhesives result in acceptable VOC levels, in Examples 4-6, the DMPD and acetone formulas evidence much lower VOC levels as a result of acetone being an exempt compound. Comparative Examples 1 and 2 in Table II show VOC levels exceeding 500 g/1 for a typical THF/resm adhesive (Comparative Example 1) and for a typical commercial cement Weld-On 711 (Comparative Example 2). The viscosity for Examples 1-6 in Table I also exemplify the low values of these DMPD base adhesives, which are commercially desirable, since they can be readily increased using thixotropic agents such as fumed silica or rheology additives such as homo-, co-, or ter-polymeπc methacrylate, MBS (methyl methacrylate-butadiene-styrene), ABS (acrylomtπle-butadiene-stryene), etc. to give de- sirable flow characteπstics and body to the adhesives

TABLE I. Results for Examples 1-6.

TABLE II. VOC & Lap Shear Strength for Comparative Examples 1 and 2.

Examples 7-15.

The compositions listed in Table III exemplify the wide latitude in formulation with based adhesives with respect to adhesive performance. Formulas of DMPD with acetone (Examples 7, 8, 11, 13); DMPD with acetone, MEK, and cyclohexanone (Example 9); DMPD with MEK and cyclohexanone (Example 12); and DMPD and MEK (Example 15) all satisfy the minimum lap shear values for 2, 16, and 72 hours as required in ASTM D-2564 for PVC.

TABLE III

Lap Shear Strength / ASTM-D2564

Examples 7-15 clearly demonstrate to one skilled in the art that vaπous changes and modifications may be used to adjust set-time, viscosity, VOC levels, bond strength and formulations costs and such changes and modifications are considered to fall withm the scope of the invention. Likewise, one skilled in the art easily recognizes that these DMPD formula- faons can be made to include other known PVC and CPVC solvents such as THF, NMP, aliphatic and aromatic ketones to further adjust desired adhesive properties. Likewise, formulation comprising vaπous molecular weight thermoplastic PVC and CPVC with DMPD blends would be obvious to one skilled in the art as exemplified in Example 13.

Examples 16-19.

Table IV below lists the solution properties of adhesives containing PVC resms having IN. values ranging from 0.68 to 0.90.

Table IV. Results for Examples 16-19.

Table IV illustrates that DMPD readily dissolves various PVC resins (of different IN ) to give 10 wt% solutions with low viscosities. This is meant to show that cements can be formulated with a range of PVC molecular weights (based on IN. value).

ASTM F-656 requires that a solvent/solvent blend is a primer if it can dissolve 10 wt% resm. li

Examples 20-23.

Table V below lists the hydrostatic burst strength of adhesives containing CPVC resins. The hydrostatic burst strengths were measured in accordance with ASTM-F493.

Table V. Results for Examples 20-23.

Table V lists some specific examples of CPVC low VOC cement formulations con- taining DMPD, MEK, and acetone. These formulations show the solvency of DMPD/MEK/acetone combinations and their effectiveness as CPVC cements. It would be obvious to one skilled in this art that other solvent blends of DMPD/MEK/acetone and other ketones such as DEK, cyclohexanone, etc., as well as formulas with minimal amounts of THF, lend themselves as cements for CPVC articles such as pipes, fittings, etc. INDUSTRIAL APPLICABILITY

The adhesives and primers disclosed herein are expected to find use in joining PVC and CPVC pipes and other such articles together.

Claims

CLAIMSWhat Is Claimed Is:

1. An adhesive for joining PVC pipes and components or CPVC pipes and components comprising either:

(al) about 5 to 25 wt% PVC resm and 0 to about 25 wt% acrylic resm, the total of said PVC resm and acrylic resm ranging from 12 to 35 wt%; or (a2) about 5 to 25 wt% CPVC resm; and (b) a solvent system comprising:

(1) 5 to 95 wt% dιmethyl-2-pιpeπdone,

(2) 15 to 75 wt% of at least one ketone selected from the group consisting of 15 to 75 wt% (1) acetone, (2) a low boiling ketone having a boiling point less than 80°C, (3) a medium boiling ketone having a boiling point withm a range of about 80° to 130°C, and (4) a high boiling ketone having a boiling point greater than 130°C, wherein said medium boiling ketone and said high boiling ketone have a maximum amount of 35 wt%,, and

(3) 0 to about 10 wt% tetrahydrofuran.

2. The adhesive of claim 1 comprising said PVC resm, wherein said PVC resm has an inherent viscosity within a range of 0.6 to 0.95.

3. The adhesive of claim 1 compπsmg said PVC resm, wherein said acrylic resm compπses a homopolymer, a copolymer or a terpolymer of methyl methacrylate having an inherent viscosity ranging from 0.1 to 1.25 or a melt flow index ranging from 1.6 to 24

4. The adhesive of claim 1 comprising said CPVC resm, wherein said CPVC resm has an inherent viscosity withm a range of 0.6 to 0.85 and a chlormation withm a range of 50 to 80 wt%.

5. The adhesive of claim 1 further comprising a filler selected from the group consisting of hollow ceramic spheres, hollow glass spheres, hollow synthetic spheres, calcium carbonate, alumina tπhydrate, calcium sulfate, and crystalline silica

6. The adhesive of claim 1 further comprising a thixotropic agent selected the group consisting of fumed silica, precipitated silica, and treated bentonite clay.

7. The adhesive of claim 1 wherein said low boiling ketones are selected from the group consisting of methyl ethyl ketone and acetone.

8. The adhesive of claim 1 wherein said medium boiling ketones are selected from the group consisting of diethyl ketone, methyl propyl ketone, methyl iso-propyl ketone, methyl iso-butyl ketone, and methyl n-butyl ketone.

9. The adhesive of claim 1 wherein said high boiling ketones are selected from the group consisting of cyclohexanone, acetophenone, methyl amyl ketone, methyl iso-amyl ketone, di-iso-butyl ketone, and ethyl amyl ketone.

10. A primer for joining PVC pipes and components or CPVC pipes and components comprising said solvent system of Claim 1.

11. A method for reducing VOC emissions in adhesives for joining PVC pipes and components or CPVC pipes and components, said method comprising mixing together said adhesive of Claim 1.