HK1028060B - Low volatile organic solvent based adhesive - Google Patents

Description

Low volatility organic solvent based adhesives

Technical Field

The present invention relates to a low Volatile Organic (VOC) solvent based adhesive. In particular, the present invention relates to a low VOC solvent based adhesive capable of bonding two thermoplastic materials together. Also, the present invention relates to a low VOC solvent-based adhesive in which the solvent evaporation rate is significantly reduced compared to solvent evaporation rates found in conventional thermoplastic solvent-based adhesives. In addition, the present invention relates to a low volatility organic solvent based adhesive having a flash point substantially above 100 ° F (as measured by the test method disclosed in ASTM D3828-87). The present invention preferably comprises a low VOC solvent based adhesive for bonding two objects or articles made of chlorinated polyvinyl chloride (CPVC). In one embodiment of the present invention, preferred solvents are naphthalene having one or more alkyl substituents and a total number of carbon atoms of 11 to 14 and/or benzene having one or more alkyl substituents and a total number of carbon atoms of 10 to 14.

Background

Solvent-based adhesives have been widely used for many years to bond thermoplastic pipes and fittings. These solvent-based adhesives provide a convenient way to easily and quickly bond thermoplastic materials. Typically, thermoplastic pipes and fittings bonded in this manner can be tested even the same day.

Generally, solvent-based adhesives include a solvent and a mixture of a resin and other additives such as thixotropic agents. The solvent-based adhesive dissolves the applied thermoplastic surface layer, allowing it to swell. The resin in the adhesive solution can facilitate the joining of the two materials to be joined, fill any voids, and reduce internal stresses. Conventional solvent-based adhesives use primary solvents including tetrahydrofuran, methyl ethyl ketone, and cyclohexanone. These solvents are very volatile and therefore the VOC content of the adhesives made therefrom is in the range 750 to 850g/l (measured by the south coast air quality management method (SCAQMD) 316A).

Furthermore, these conventional solvent-based adhesives are preferably pretreated with a primer such as tetrahydrofuran or a cleaner such as acetone in order to minimize adhesive failure prior to application. During the cleaning process, more volatile organic compounds are released into the atmosphere. Furthermore, because these conventional solvent-based adhesives are formed from a large amount of solvent, when applied to thermoplastic materials, the solvent spreads over a large area and drips, resulting in additional volatilization. In addition, conventional solvent-based adhesives and/or primers used in such adhesives have very low flash points. Low flash points require special precautions during handling and packaging to avoid burning of these adhesives and/or primers. The solvent evaporated from the solvent-based adhesive causes environmental pollution problems.

Us patent 3,726,826 discloses a stable binder solution for polyvinyl chloride. The solution comprises 5 to 25 weight percent of chlorinated polyvinyl chloride resin in tetrahydrofuran and 0.4 to about 5 weight percent of 1, 2-butylene oxide.

Us patent 4,098,719(Hushbeck) describes a primer for use in the assembly of polyvinyl chloride pipes and tubes or of PVC pipes and tubes with Acrylonitrile Butadiene Styrene (ABS) pipes or tubes. The primer consists essentially of from 0.5 to 2.5 weight percent of a non-plastic polyvinyl chloride resin dissolved in a solvent. The solvent is a mixture of tetrahydrofuran and dimethylformamide.

Further examples of conventional solvent-based adhesives are found in european patent application 0489485 a1(Texaco chemical company). This application discloses a method of welding plastics by applying alkylene carbonate in pure form or in admixture with a co-solvent such as aromatic hydrocarbons, ketones, esters, ethers, glycol ethers, imidazoles, tetramethylurea, N' -dimethylethyleneurea, 1, 1, 1-trichloroethane and N-methylpyrrolidone.

In addition, U.S. patent 4,910,244 describes a storage stable CPVC-containing adhesive. The solvent-based adhesive includes 5 to 30 weight percent CPVC and 95 to 70 weight percent organic solvent and stabilizer. The stability of the mixture is improved when stored in tin-coated steel containers.

As described above with reference to the conventional solvent-based adhesives, these adhesives typically have a low solids content. These adhesives are also volatile and flammable because the highly volatile and low flash point solvents make up a significant portion of the adhesive.

Due to the environmental awareness that exists today, laws and regulations dictate that the VOC content of all materials, especially solvent-based adhesives, be limited. For example, in california, the South Coast Air Quality Management (SCAQMD) method has enacted relevant regulations, defining the VOC content of the materials used to bond thermoplastics. For example, the VOC limit of CPVC and/or polyvinyl chloride (PVC) solvent-based adhesives, as defined by regulation 1168 of SCAQMD, that 1/1/94 begins to work, is 450 grams/liter (as determined by the SCAQMD316A method). The VOC limit for acrylonitrile-styrene-butadiene (ABS) solvent-based adhesives was 350g/l from 1/1994 (SCAQMD316A method determination). The laws laid down next step reduce these limits even further. In the upcoming regulations, it is expected that the VOC limit for the PVC solvent-based adhesive of SCAQMD will be 250 grams/liter, while the VOC limit for the ABS solvent-based adhesive of SCAQMD will be maintained at 350 grams/liter.

There have been some adhesive formulations that contain lower VOC levels than traditional solvent-based adhesive systems. It is believed that the VOC value of conventional solvent-based adhesives was generally about 650 g/l (SCAQMD316A assay) before 1994. For example, Australian patent application 86750/91 discloses an adhesive comprising more than 80% by weight N-methyl-2-pyrrolidone, more than 0.25% by weight of a viscosity modifier which may be silica, a thickener or a thixotropic agent and more than 10% by weight of a vinyl polymer. Similarly, U.S. Pat. No. 4,675,354 discloses a dope comprising a solution of a water-insoluble synthetic organic polymer in a solvent such as N-methyl-2-pyrrolidone. The glue solution can be used at a higher temperature without the problems caused by solvent vapor and fire hazards.

Further, U.S. Pat. No. 4,687,798 discloses a liquid cement for bonding water-insoluble polymers. The liquid cement includes about 10-15% by weight of a water insoluble polymer and a solvent. The solvent includes ethyl acetate and N-methyl-2-pyrrolidone. The ethyl acetate in the solvent ranges from about 3% to about 50% by weight, with the remainder being N-methyl-2-pyrrolidone.

Furthermore, european patent application 0547593 a1 discloses a low VOC adhesive composition. The composition of the European patent application comprises a mixture of from about 5% to about 60% by weight of at least one water-insoluble polymer, from about 1% to about 30% by weight of inorganic or synthetic resin hollow microspheres, and from about 20% to about 70% by weight of at least one volatile organic liquid which is a solvent for the water-insoluble polymer.

U.S. patent 5,470,894(Patel et al) provides another example of a low VOC solvent based adhesive. The low VOC solvent based adhesives in this patent are used to bond CPVC pipe. The adhesive comprises a high vapor pressure solvent consisting of from about 15 to 35 weight percent tetrahydrofuran and from 0 to about 30 weight percent methyl ethyl ketone; a low vapor pressure solvent consisting of from about 20 to 45 weight percent cyclohexanone, from 0 to about 30 weight percent N-methylpyrrolidone, and from 0 to 10 weight percent dibasic acid ester. Patel et al claim that their adhesives have VOC levels of 450 grams/liter or less and that the adhesives meet or exceed desired performance criteria such as hydrostatic burst strength and sustained hydrostatic pressure tests.

However, there are environmental problems with the use of any of the above listed adhesives. There are several alternatives to solvent-based adhesives. They are mechanical, reactive and thermal bonding systems. Generally, mechanical joining systems are the most widely used methods. Examples of mechanical joining systems include Acorn tubing from Hepworth Building Products, PolyGrip tubing from Philmac Corporation, and Uncopper tubing from Genva. Thermal joining systems are difficult to predict due to the constant difficulty in producing suitable pipe/tube joints. Examples of thermal bonding systems include hot melt adhesives available from Minnesota, Mining and Manufacturing companies. Thermal bonding systems are more difficult to construct and have been used less often than solvent-based adhesives. Examples of reactive bonding systems include epoxy resins. Epoxy resins are available from Noble Corporation under the name of Copper Bond. Other examples of epoxy resins include general purpose polyurethanes, high shear strength polyurethanes and universal polyurethanes available from the company Hardman Corporation. However, these reaction joining systems also have problems in that they have a long curing time and are poor in strength upon rigid joining. Their efficacy is also temperature dependent, and the curing times of epoxy materials are very long at low temperatures. Furthermore, there may be chemical reaction products that can compromise the strength of the tube. Although these alternatives exist, they are expensive, time consuming and inconvenient.

While there are some environmental quality issues, it is beneficial to continue to use solvent-based adhesives to bond thermoplastic materials. First, solvent-based adhesives are easy to use, and many workers have experience with such adhesive systems for many years. Second, the solvent-based adhesives are inexpensive to produce and have a long service life once the two thermoplastic materials are bonded together with the adhesive. Third, the two thermoplastics can be bonded in situ with a solvent-based adhesive without any additional equipment. Fourth, the solvent-based adhesive system cures rather quickly, allowing for testing performance. In addition, solvent is applied using one technique for all sizes of tubing. In general, if the solvent-based adhesive system meets Underwriter laboratory test 1821, the solvent-based adhesive may be applied to the joint at any temperature in the range of 0 to 120 ° F. Also, the efficacy of solvent-based adhesive systems is not dependent on chemical reactions. Furthermore, solvent-based adhesive systems can be stored at ambient temperatures for extended periods of time. Thus, solvent-based adhesive systems are generally practical and economical.

For example, there is a need for a low solvent based adhesive with a reasonable shelf life. And there is a need for a low VOC solvent based adhesive that meets the performance criteria required to bond two thermoplastic materials together. Additionally, there is a need for a low VOC solvent-based adhesive system having a flash point higher than that of conventional solvent-based adhesives and/or adhesive primers.

Summary of The Invention

The present invention includes a novel low VOC solvent based adhesive comprising a mixture of two or more volatile organic solvents and a resin. The novel low VOC solvent based adhesives may optionally contain thixotropic agents such as silica. The novel low VOC solvent based adhesive preferably comprises about 5 to 20 weight percent thermoplastic resin, about 38 to 75 weight percent substituted naphthalene and/or substituted benzene with one or more alkyl substituents and/or N-methyl-2-pyrrolidone, about 20 to 45 weight percent dimethyl adipate, and optionally about 1.5 to 2 weight percent silica, based on the weight of said solvent based adhesive. More preferably, the novel low VOC solvent based adhesives have a flash point in excess of 100 DEG F (as measured by ASTM 3828-87).

In a further embodiment of the invention, the invention comprises a novel low VOC solvent based adhesive having a flash point substantially greater than 100F (as measured by ASTM 3828-87). The novel low VOC solvent based adhesive preferably comprises from about 5 to about 20 weight percent of a thermoplastic resin, from about 38 to about 75 weight percent of N-methyl-2-pyrrolidone and/or substituted naphthalene and/or alkyl substituted benzene of 10 to 14 carbon atoms, from about 15 or 20 to about 45 weight percent dimethyl adipate and optionally from about 1.5 to about 2 weight percent silica and optionally from about 5 to about 10 weight percent of a ketone having a flash point greater than 70 DEG F and preferably greater than 100 DEG F. The ketone is preferably 5-methyl-2-hexanone (methyl isoamyl ketone) or 4-methyl-2-pentanone (methyl isobutyl ketone) or a combination thereof.

The low VOC solvent based adhesives of the present invention have a VOC content of less than 450 grams per liter (SCAQMD316A assay). Preferably, the VOC content of the novel low VOC additive binder is less than 350g/l, and preferably less than 250g/l (SCAQMD316A determination).

Detailed Description

The low VOC solvent-based adhesives of the present invention comprise a mixture of two or more volatile organic solvents that evaporate at ambient temperature and a thermoplastic resin. And the low VOC solvent based adhesives of the invention preferably have a flash point greater than 100 ° F (as measured by ASTM 3828-87). Other ingredients, including other solvents, fillers, thixotropic agents or stabilizers may be added to the low VOC solvent based adhesive as desired. The low VOC solvent-based adhesives described herein are further summarized as having the following characteristics: the viscosity is from 500 to 3000 centipoise. Initial strength of about 1-3 minutes, binder solids content of less than 20% by weight, shelf life in non-reactive containers, and cure time can vary. By fine tuning the ratio of solvents used, the curing time can vary from end use to end use.

The first, second and optional auxiliary solvents are mixed in proportions (as described in more detail below) such that the low volatile organic content is less than 450g/l, preferably less than 400g/l, more preferably less than 350 or 300g/l, and preferably less than 250g/l as determined by the South Coast Air Quality Management (SCAQMD) test method 316A. In one embodiment, the total volatile organic content is desirably from about 50 or 100 to about 150, 200, or 250 g/l. Since SCAQMD is considering revising their defined standards, the volatile organics reported by test method 316A do not include the weight percent of volatile acetone, and thus the volatile organic content ranges described above optionally do not include any contribution of acetone in the solvent-based binder to the volatile organics.

The flash point of a material is a property considered as relating to the overall flammability of the material. One method of determining the flash point of a material is ASTM 3828-87, which is incorporated by reference herein in its entirety. Flash points are used to define flammable and combustible materials in safety and transportation regulations such as CFR § 173.120 and § 173.150. These regulatory regulations specify the type of packaging required for these materials. If the flash point of the material is high, the packaging and shipping requirements are not as stringent as those typically required for liquid cement and/or primer. Adhesives having flash points above 100F may be packaged and shipped in less expensive plastic (e.g., polyolefin) containers as specified by the U.S. transportation regulatory agency, while similar adhesives having lower flash points require more expensive metal containers.

Thermoplastic resins useful in forming the low VOC solvent-based adhesives of the present invention include polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), poly (acrylonitrile-butadiene-styrene) (ABS), polystyrene, and other amorphous thermoplastic resins that are soluble in a mixture of two or more volatile organic solvents. The solvent-based adhesives of the present invention generally use the same resins as the thermoplastic materials to be bonded when they are molded. Preferably the resin is CPVC, PVC or ABS. The amount of thermoplastic resin added to the low VOC solvent-based adhesive preferably ranges from about 5 to about 15 or 20 weight percent, more preferably from about 10 to about 13.5 or 15 weight percent. Examples of ABS resins that may be used include Cycolac ABS resin from GE plastics and Lustran ABS resin from Monsanto. The resin used in the low VOC solvent based adhesive is most preferably CPVC.

The inherent viscosity of the CPVC and/or PVC should be in the range of about 0.6 to 0.96. Preferably, the degree of chlorination of the CPVC resin should be in the range of from about 58 to 72 weight percent. Preferably, the PVC resin should have a degree of chlorination of less than 57% by weight. In general, the CPVC resin used is the CPVC resin defined in 23477 class of ASTM D1784. However, the molecular weight of the CPVC resin should not be less than 0.68 IV (inherent viscosity). Examples of CPVC suitable for use in the present invention include Temprite 674 x 571 and Temprite 677 x 670 CPVC, both from b.f. goodrich company (Temprite is a registered trademark of b.f. goodrich company).

In addition to thermoplastic resins, the low VOC solvent-based adhesives of the present invention also include a mixture of two or more volatile organic liquid solvents that can evaporate at ambient temperature. The first solvent used in the mixture is a low vapor pressure solvent. Alkyl-substituted naphthalenes having one or more alkyl groups and a total carbon number of 11 to 14 and/or alkyl-substituted benzenes having one or more alkyl groups and a carbon number of 10 to 14 and/or N-methyl-2-pyrrolidone (NMP) are the most preferred low vapor pressure solvents. Preferred benzenes are those having 2 or more, 3 or more and 4 or more alkyl substituents. NMP is a commercial product from Aldrich Chemical, Ashland, BASF, Chemoxy International and Janssen Chemical. Alkyl-substituted naphthalenes and alkyl-substituted benzenes having one or more alkyl groups may be obtained as separate fractions from petroleum distillation processes. They are available from Koch specialty chemical group (corpus christi, Texas) under chemical name such as methylnaphthalene or as specific Sure Sol  products (mainly for alkyl substituted benzenes). They are generally classified as specialty chemicals, while benzene, toluene, xylene, cumene and ethylbenzene are generally classified as common commercial products. The first organic liquid solvent is present in the novel binder in a proportion ranging from about 38 to about 70 or 75% by weight, preferably from 38 to about 65% by weight. In one embodiment, 50% by weight of NMP is present in the low VOC solvent based adhesive.

It is desirable to formulate low VOC adhesive products with little or no NMP. NMP is a hygroscopic substance (absorbs moisture) and is less desirable during application. In addition to adsorbing moisture, metal containers holding solvent-based adhesives can be corroded, and the corrosion product iron oxide can dehalogenate PVC or CPVC, leading to undesirable gelling of the stored adhesive. In Table 6, the reason for the failure in storage stability of the NMP-based adhesive is suspected to be gelation. Thus, in some embodiments, NMP is desirably less than 10 weight percent, more desirably less than 5 weight percent, and most desirably less than 1 weight percent, based on the weight of the solvent-based binder.

In one embodiment, preferably at least about 38 to about 65, 70, or 75 weight percent of the low vapor pressure solvent portion, more specifically at least 5 weight percent of the solvent-based binder comprises said one or more alkyl substituted naphthalenes or substituted benzenes having one or more alkyl groups or combinations thereof, preferably from about 20 to about 65, 70, or 75 weight percent of the binder, and preferably from about 38 or 50 to about 65, 70, or 75 weight percent.

In addition to the NMP, alkyl substituted naphthalene, and alkyl substituted benzene, other co-solvents may be present in an amount of from about 5 to about 47 weight percent. These other solvents are preferably present in an amount of from about 15, 20 or 25 to about 45 or 47 weight percent, based on the weight of the solvent-based adhesive. The auxiliary solvent may include a second solvent and optionally a third solvent or more. In a preferred embodiment, the total amount of any one or more co-solvents having a flash point of less than 37.8 ℃ (100 ° F) as measured by ASTM D3828-87 is less than 10% by weight, and the volatile organic content as measured by test method 316A is less than 350 g/l.

The second organic liquid solvent in the solvent-based adhesive is selected from the group consisting of polycarboxylic acids preferably having from 4 to 15 carbon atoms, and polycarboxylic acid mono-and di-basic esters preferably having up to 19 carbon atoms, such as pimelic acid, monomethyl glutarate, monomethyl pimelate, monomethyl azelate, monomethyl sebacate, monomethyl adipate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl pimelate, dimethyl suberate, and dimethyl azelate; or else acid chlorides of polycarboxylic acids preferably having from 4 to 15 carbon atoms, such as glutaryl chloride, adipoyl chloride and pimeloyl chloride; and an alkanoylchloride compound of the polycarboxylic acid having up to 17 carbon atoms, such as chloroadipyl chloride, chloropimeloyl chloride and the like; or a mixture thereof. For example, a mixture of dimethyl glutarate, dimethyl adipate and dimethyl succinate may be used. An example of such a mixture that is commercially available is DBE-9 available from Dupont chemical company. The most preferred second organic solvent is dimethyl adipate ("DMA"). DMA is commercially available from Dupont chemical company under the DBE-6 trade name. DBE-6 is believed to be a mixture comprising 98.7 weight percent DMA, < 0.5 weight percent dimethyl glutarate and < 0.1 weight percent dimethyl succinate. The amount of ester of a polycarboxylic acid with an alkanol and/or acid chloride of a polycarboxylic acid is preferably from about 10 to about 35% by weight, based on the weight of the binder. In another embodiment, the second organic solvent is present in the solvent mixture in a range of about 20% to 45% by weight. In the most preferred embodiment, 27 weight percent DMA is used in the low VOC solvent based adhesive.

The low VOC solvent-based adhesive may also include other optional ingredients. For example, the low VOC solvent-based adhesives of the present invention include small amounts of other optional solvents that do not raise the VOC content to 450 grams per liter and are miscible with two or more volatile liquid organic solvents. Examples of useful solvents include cyclic or straight chain ketones, esters of monocarboxylic acids with alkanols, halogen-containing solvents, ethers and other solvents such as Dimethylformamide (DMF) and Dimethylsulfoxide (DMSO).

Ketones useful as co-solvents in the present invention include acetone, methyl ethyl ketone, methyl isoamyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone, and other ketones having 3 to 15 carbon atoms. These ketones are desirably present in an amount of about 15% by weight or less based on the weight of the solvent-based adhesive, and preferably from about 5 to about 10% by weight. It is desirable that the flash point of one or more of the secondary solvents, and especially the ketone, be all above 70 or 100F. An important requirement is that the flash point of all ketones when mixed into a ketone blend is preferably above a specified value. In another embodiment, the amount of solvent, such as ketone, having a flash point of less than 50F is preferably limited to within 5% by weight.

Examples of esters of monocarboxylic acids having 2 to 15 carbon atoms and alkanols having 1 to 15 carbon atoms which may be used in the present invention include methyl acetate, Ethyl Acetate (EA), ethyl formate, ethyl propionate and butyl acetate. Useful halogen-containing solvents include dichloromethane, dichloroethane, and trichloroethane. Ethylcellulose-derived ethers are viable examples of ethers of 3 to 15 carbon atoms, which can be added as co-solvents. Other liquids that may be employed as co-solvents include tetrahydrofuran and any other high vapor pressure solvent that meets the requirements including, but not limited to, the above initial strength and desired flash point. Generally, these other liquids are added for the purpose of accelerating the curing time and the evaporation process.

Any material known in the art to function as an inert filler may be used as a filler in the present invention. Examples of the filler optionally used in the present invention include hollow microspheres (glass or ceramic), polymers, glass spheres, magnesium silicate, magnesium oxide, shell powder, alumina, talc, barium sulfate, calcium carbonate and other fine powders. These fillers are typically added to the composition in amounts of about 0.05 to 20% by weight. Fillers are added for the purpose of reducing cost, maintaining viscosity, or slightly reducing VOC. Preferred fillers include polymers and calcium carbonate.

The low VOC solvent-based adhesive may also optionally include a thixotropic agent in the composition. Examples of useful thixotropic agents include fumed silica, precipitated silica, bentonite, quartz flour, mica, ethyl cellulose, hydrogenated castor oil, organically modified clays, other thickeners, or viscosity modifiers. Preferred thixotropic agents include fumed silica. Generally, if a thixotropic agent is to be used, it is used in an amount ranging from about 1 to about 3 percent by weight, preferably from about 1.5 to about 2 percent by weight, based on the weight of the solvent-based adhesive.

Also, pigments, dyes, dispersants, or colorants may be added to the low VOC solvent-based binder. Examples of useful pigments include titanium dioxide, calcium carbonate or carbon black. The pigment is generally used in an amount ranging from 0.05% to 5.0% by weight based on the weight of the solvent-based binder.

The low VOC solvent-based adhesive may include other additives, including any additives known to those skilled in the art. Suitable additives include, for example, but are not limited to, various stabilizers, antioxidants, antistatic agents, smoke suppressants, moisture scavengers, and acid scavengers. Since several additives can be combined in many different ways, the amount of additive will vary from application to application. The optimization of a particular additive composition can be determined by techniques conventional in the art. Additives are typically added in amounts of from about 0.5% to 1.0% by weight, based on the weight of the low VOC solvent-based adhesive.

The components of the low VOC solvent-based adhesive may be combined in any convenient manner. For example, all components are mixed homogeneously with a mixing device such as a mixer. Preferably, the two solvents are mixed first, without the need for a special procedure or sequence. The thermoplastic resin and thixotropic agent are then added to the solvent mixture without requiring a particular order. The solid is rapidly dissolved in the solvent using an agitated Mixer such as a Grenier Mixer model 3002 with rapid agitation. The mixer was operated at 400-500rpm for 10-15 minutes. The mixture can then be placed on a slow moving roll mixer to blend the compositions homogeneously. An example of a roller mixer that can be used is Paul o. The mixture was treated in a Ball Mill at 160rpm for about 1 hour.

Any application method may be used to apply the low VOC solvent based adhesive to the two thermoplastic articles to be bonded. The surface of the article near the point of attachment may be wiped with a brush or cloth containing acetone or other solvent prior to application of the low VOC solvent-based adhesive of the present invention, but this step is not necessary. The low VOC solvent-based adhesive may be applied using any method known in the art. Preferably, a low VOC solvent based adhesive is applied with a single applicator adjacent the bonding surfaces of two thermoplastic articles to be bonded, and a uniform layer of adhesive is applied to both surfaces. Generally, the coating thickness on both surfaces is about 1/2 to 1mil (0.01mm-0.025 mm). The joints were then assembled, cured and tested.

Low VOC solvent-based adhesives have many applications. For example, low VOC solvent based adhesives can be used to bond thermoplastic pipes and tubing for a variety of purposes, such as pump systems, hot and cold water dispensing systems, sprinkler systems, spas, fire sprinkler systems, drains, sewage systems, and exhaust system applications. The low VOC solvent based adhesive is suitable for any other thermoplastic material that can be bonded. Preferred thermoplastic pipes are CPVC, PVC, ABS and polystyrene. Although the solvent-based adhesive was formulated as a one-component adhesive, i.e., no primer or solvent pretreatment was required, in some tests, the performance was improved by pretreatment with a primer or solvent, e.g., cleaning ABS tubing with acetone. Typically, solvent-based adhesives contain a small amount of the pre-treatment solvent recommended for each type of pipe, for example, acetone as the ABS improves the properties of the adhesive itself. The following examples serve to illustrate the invention in further detail.

Examples

In the examples of tables 1-5 below, NMP-based low VOC solvent-based adhesives were formulated. Generally, the first step is to determine the desired VOC content. The desired VOC content is determined by the choice of the two solvents (and the co-solvents used). The VOC constant for each solvent to be used for the low VOC solvent-based adhesive was experimentally determined using the SCAQMD316A method. The VOC estimation constant for a solvent-based adhesive can then be determined using the following equation: (VOC constant of solvent 1 x% solvent 1 by weight of the total solvent of the solvent-based adhesive)) + (VOC constant of solvent 2 x% solvent 2 by weight of the total solvent of the solvent-based adhesive)) + (VOC constant of solvent 2 by weight of the total solvent of the solvent-based adhesive), if an auxiliary solvent is used in the mixture, the auxiliary solvent is similarly calculated and added to solvent 1 and solvent 2. Once the desired VOC constant is determined, a low VOC solvent based adhesive can be formulated to alter the VOC content using the SCAQMD316A method. The viscosity of the liquid cement is optimized by the addition of a thixotropic agent. The green strength and cure time are varied by adjusting the solvent ratio while still maintaining the desired VOC content and viscosity.

The curing time can be varied to match the needs of the end use. In the first set of examples (tables 1-5), the amounts of NMP and dimethyl adipate (DMA) were varied. The following examples are all tested for VOC content, cure time, green strength and rapid failure. The VOC content was determined using the SCAQMD316A test method, the quick failure was determined using the ASTM 1599 method, and the cure time was determined using the Underwriters laboratories method UL 1821.

Through certain steps, the tester tries to pull or unscrew the combined pipe and pipe fitting for initial strength test. During this step, the inside of the thermoplastic tube and the outside of the thermoplastic tube (the insert tube) are each coated with the same adhesive. After 1 minute, the tester tries to pull the two apart or unscrew them. The combined pipe and tubing was typically subjected to a torque of 6 ft-lbs. during the test. If the two are not separable, they are defined as "unzipped", meaning that the test is repeated until a "unzipped" result is obtained. For each repeat of the experiment, 1 additional minute was added to the previous time. The time to "pull-off" represents the initial intensity. Unless otherwise noted, the tubing used to form the tabulated data was SDR-11, also known as 3/4 inch tubing, with an inner diameter of 0.875 inch to 0.878 inch and a wall thickness of 0.080 inch to 0.100 inch.

Examples of commercially available liquid cements with comparable and widely differing inherent viscosities include Orange low VOC medium thick CPVC cement (one-step) and two-step cement available from Oatey, and welded CPVC2714 available from IPS^TMOrange dense cement (one-step) and two-step cement. Generally, the VOC content of commercial one-step liquid cements is about 450g/l, whereas the VOC content of two-step cements is greater than 650 g/l.

TABLE 1
										Examples	DMA	NMP	Silicon oxide	TempRite674×571 CPVC	VOC(g/l)	Initial strength (minutes)	Viscosity (cp)	Quick rupture (psi)	DMA/NMP ratio
1	20	65	2	13	154	2	1445	≥1400	0.31
										2	30	55	2	13	143	1	2585	≥1400	0.55
3	40	45	2	13	164	1	9285	≥1400	0.89
										4	45	40	2	13	128	1	69950	≥1400	1.125
										Commercially available liquid cement					≥400	1-2	500-3000	Pipe or 1400 or more

Examples 1 to 4 illustrate that the VOC content of solvent-based adhesives formulated with DMA/NMP ratios from 0.31 to 1.125 is lower than that of standard liquid cement formulations. Examples 3 and 4 are still effective as adhesives, but are less acceptable for industrial use due to their higher viscosity.

TABLE 2
															Examples	DMA	NMP	Silicon oxide	TempRite674×571 CPVC	Cyclohexanone	MEK	THF	EA1	MEOH	VOC(g/l)	DMA/NAP ratio	Initial strength (minutes)	Viscosity (cp)	Quick rupture (psi)
5	20	60	1	13					6	278	0.33	2	1940	≥1400
															6	20	60	1	13	6					274	0.33	2	1672	785PF2
7	26	55	1	13			5			267	0.47	3	1872	825PF
															8	25	55	1	13	2	2	2			261	0.45	2	2136	850PF
9	26	55	1	13	5					268	0.47	1	1485	≥1400
															10	26	55	1	13		5				239	0.47	2	1130	≥1400
11	30	50	2	13			5			250	0.60	2	2996	743PF
															12	30	50	2	13		5				278	0.60	2	2992	938PF
13	30	50	2	13	5					283	0.60	1	2830	≥1400
															14	30	50	2	13				5		250	0.60	2	2810	≥1400
15	45	35	2	13				5		293	1.29	3	54000	938PF
															16	45	35	2	13			5			257	1.29	2	11140	900PF
17	45	35	2	13	5					232	1.29	3	10020	935PF
															18	45	35	2	13		5				253	1.29	12	78700	≥1700PF
19	20	60	1	13				6		363	0.33	2	604	≥1400
															20	20	60	1	13	6					321	0.33	2	580	1650PF
21	20	60	1	13		6				362	0.33	1	245	1625PF
															22	20	60	1	13			6			341	0.33	1	300	≥1400PF

TABLE 2
															Examples	DMA	NMP	Silicon oxide	TempRite674×571 CPVC	Cyclohexanone	MEK	THF	EA1	MEOH	VOC(g/l)	DMA/NMP ratio	Initial strength (minutes)	Viscosity (cp)	Quick rupture (psi)
23	25	50	1	15			9			355	0.50	2	1112	1800PF
															24	25	50	1	14		9				281	0.50	2	1468	675PF
Commercially available liquid cement										≥400		1-2	500-3000	More than or equal to 1400 or pipe damage

¹EA is ethyl acetate²PF refers to pipe failure prior to adhesive failure

Examples 5 to 24 in Table 2 illustrate solvent-based adhesives having a DMA/NMP ratio of from 0.31 to 1.125 and a VOC content of less than 400 grams/liter with a small amount of the third solvent or combination of solvents in a small portion (< 10% by weight) of the total formulation and performing in the same manner as existing commercially available solvent-based adhesives having a VOC content above 450 grams/liter.

In these examples, the VOC content was all below 300g/l and the bond strength passed all the requirements listed above. Formulations 15, 16, 17 and 18, while still effective as adhesives, are less acceptable for industrial use due to their higher viscosity.

TABLE 3
															Examples	DMA	NMP	Silicon oxide	TempRite677×670CPVC	TempRite674×571CPVC	Cyclohexanone	MEK	THF	EA	VOC(g/l)	Initial strength (minutes)	Snap break (psi)	Viscosity (cp)	DMA/NMP ratio
25	20	60	1	13					6	363	2	≥1400	604	0.33
															26	20	60	1		13				6	308	2	≥1400	1904	0.33
27	20	60	1	13		6				321	2	1650PF	580	0.33
															28	20	60	1		13	6				274	2	785PF	1672	0.33
29	20	60	1	13			6			362	1	1625PF	245	0.33
															30	20	60	1		13		6			314	1	≥1400PF	885	0.33
31	20	60	1	13				6		341	1	≥1400PF	300	0.33
															32	20	60	1		13			6		337	1	≥1400PF	975	0.33
Commercially available liquid cement										≥400	1-2	Not less than 1400psi or pipe failure	500-3000

Examples 25 to 32 in Table 3 illustrate that low VOC solvent-based adhesives having a DMA/NMP ratio of 0.3 and a total formulation of 10 wt.% or less of the third solvent have a relatively low VOC and perform as well as existing commercially available solvent-based adhesives. And, if lower molecular weight CPVCs (e.g., Temprite) are used in the formulation^TM677X 670 CPVC) resin, the viscosity can be improved and the performance is superior to existing solvent based adhesives.

TABLE 4
										Examples	TempRite674×571 CPVC	Silicon oxide	NMP	MEK	DMA	VOC(g/l)	Viscosity (cp)	Quick rupture (psi)	DMA/NMP ratio
33	12	2	41	10	35	287	1460	≥1400PF	0.86
										34	11.5	1.5	43	10	34	213	1200	≥1400PF	0.8
35	11.5	1.5	39	10	38	289	1325	≥1400PF	0.97
										36	11.5	1.5	47	10	30	271	810	≥1400PF	0.64
37	13.5	1.5	43	10	32	274	1975	≥1400PF	0.74
										38	13.5	1.5	50	8	27	201	1840	≥1400PF	0.54
39	13.5	1.5	48	8	29	243	1890	≥1400PF	0.6
										40	10	2	44	10	34	252	610	≥1400PF	0.77
41	12.5	1.5	40	10	36	269	1950	≥1400PF	0.9
										42	12.5	1.5	41	8	37	244	3305	≥1400PF	0.9
43	13.5	1.5	41	10	34	242	4210	≥1400PF	0.82

Examples 33 to 43 illustrate that solvent-based adhesives having a DMA/NMP ratio of from 0.54 to 0.97 and a small amount of MEK (2-butanone) component present in an amount ≦ 10 wt.% of the total formulation have a lower VOC content than commercially available solvent-based adhesives (VOC content of 450 g/liter or more) and perform as well as these commercially available solvent-based adhesives.

Also, example 38 illustrates that solvent-based adhesives having a DMA/NMP ratio of less than 0.55 and a small amount of MEK (2-butanone) component in an amount less than or equal to 8 weight percent of the total formulation have a VOC content of 201 grams per liter and perform as well as these conventional solvent-based adhesives.

In the following example, example 44, the following components were used: 50 wt.% NMP30 wt.% DBE-6(DMA), 5 wt.% butanone, 13 wt.% Temprite 674X 571 CPVC resin, 2 wt.% silica performance

Adhesive matrix	VOC (g/l) for various substrates	Rapid destruction (psi) of various substrates
			CPVC	250	938-pipe destruction
PVC	168	1575-tube destruction
			ABS	169	375-tube failure

The VOC content of the solvent-based adhesive system is determined by adopting an SCAQMD316A method; rapid failure was determined using ASTM D-1599 method. The following properties were obtained:

maintaining long term hydrostatic pressure at elevated temperatures (150F, 370psi tube pressure, minimum 1000 hours duration) -ASTM D-2837

The 1 "module 1158 hours was not destroyed.

The 3 "component 1315 hours was not destroyed.

Viscosity (Brookfield): 2792cp (Brookfield viscometer, spindle 5, 100rpm)

Initial strength: 2 minutes

Lab shearing: 148-UL 1821

Curing time:

73 ℃ F. for 7 minutes

28 ℃ F. for 20 min

0 ℃ F. (clean with acetone) 45 min

Tendency to stress cracking:

after 20 hours a darkening of the panel was observed

After 202 hours, edge swelling of the panel was observed.

The test was discontinued.

The above-mentioned stress cracking tendency of the sample was measured in the following manner. Samples with dimensions of 7cm by 3mm by 1.25cm were prepared from the compression molded plaques. These samples were inserted into a tester as described in FIG. 1 of the article "stress cracking of rigid polyvinyl chloride by plasticizer migration" published in the journal of vinyl technology, Vol.6, 4, published 12.1984. The sample was inserted into the tester using a vice. The sample was placed on the edge of the vise, approximately half way across the width extending beyond the vise edge. The sample was then bent with vice until its ends were close enough to slide into the edge of the tester. After the sample was placed in the tester, a low VOC solvent based adhesive was applied to the sample with a medical dropper. The samples were periodically removed from the chemicals and inspected for signs of cracking, crazing, or discoloration. The test was carried out until material failure was observed.

In the following examples, the first organic liquid solvent used was NMP. The second organic liquid solvent is selected from the group consisting essentially of pimelic acid, monomethyl glutarate, monomethyl pimelate, monomethyl azelate, monomethyl sebacate, monomethyl adipate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl pimelate, dimethyl suberate and dimethyl azelate, glutaryl chloride, adipoyl chloride and pimeloyl chloride or mixtures thereof. The VOC content, initial strength and rapid failure were determined for each combination as shown in table 5.

TABLE 5
									Examples	Subdivision of	Amount of addition	NMP	Silicon oxide	Temrite 674X 571 CPVC resin	VOC(g/l)	Initial strength (minutes)	Quick break (psi)
45	Pimelic acid	19.5	72.9	1.4	6.2	283	1	1375F
									46	Glutaric acid monomethyl ester	27	62	2	9	253	1	1200F
47	Pimelic acid monomethyl ester	25	65.6	1.9	7.5	158	1	1150F
									48	Azelaic acid monomethyl ester	40	45	3	12	121	3	＞1400gel
49	Sebacic acid monomethyl ester	40	45	3	12	137	3	＞1400gel
									50	Adipic acid monoethyl ester	30.8	57.7	2.3	9.2	179	3	1000F
51	Succinic acid dimethyl ester	40	45	3	12	341
									52	Glutaric acid dimethyl ester	40	45	3	12	289
53	Adipic acid dimethyl ester	40	45	3	12	152
									54	Pimelic acid dimethyl ester	40	62	2	9	241	1	1450F
55	Suberic acid dimethyl ester	40	45	3	12	77	2	＞1400
									56	Azelaic acid dimethyl ester	40	45	3	12	114	2	＞1400
57	Glutaryl chloride	27	62	2	9	197	1	1175P
									58	Adipic acid dichloride	27.6	62.1	2.1	8.3	83	2	1400F
59	G typeDiacid chlorides	27	62	2	9	178	2	1100F

The data in Table 5 show that when NMP is used in combination with one of the second organic liquid solvents listed above, an adhesive composition with suitable properties is obtained.

The following three examples are related to the determination of the flash point of the novel low VOC solvent based adhesives of the present invention. The flash point of the composition was determined in an RT-1 model Erdco flash tester according to ASTM D3828-87. The following results were obtained: component A

13.5% TempRite 674X 571 CPVC resin

1.5% silicon oxide

27％ DMA

58％ NMP

Flash point: 203 DEG F

The VOC content determined by SCAQMD316A was 153g/l of component B:

13.5% TempRite 674X 571 CPVC resin

1.5% silicon oxide

27％ DMA

50％ NMP

8.0% 5-methyl-2-hexanone (CAS # 110-12-3), available from Aldrich chemical Co

And (4) obtaining.

Flash point: 167 deg. F

The VOC content determined by SCAQMD316A was 240g/l component C:

13.5% TempRite 674X 571 CPVC resin

1.5% silicon oxide

27％ DMA

50％ NMP

8.0% 4-methyl-2-pentanone (CAS # 108-10-1), available from Aldrich chemical company.

Flash point: 131 degree F

The VOC content determined by SCAQMD316A was 215 g/l.

In contrast, the following flash points for commercially available one-step and two-step liquid cements were obtained:

standard Oatey one-step "low VOC" liquid cement: fp: -20 ℃ or-4 ℃ F

Standard Oatey two-step "low VOC" liquid cement: fp: -15 ℃ or +5 ℃ F

Pure tetrahydrofuran at-17 ℃ or 1 DEG F

Pure cyclohexanone at 67 ℃ or 154 DEG F

Pure MEK (2-butanone) -3 ℃ or 26 DEG F

The examples in table 6 below illustrate that substituted naphthalenes of 11 to 14 carbon atoms and/or substituted benzenes of 10 to 14 carbon atoms can be used in place of NMP in low VOC liquid cements, resulting in lower VOC values (e.g., as low as 73g/l) as measured by SCAQMD316A, and meeting the physical property tests for solvent-based adhesives. The flash point of the example using 8% MEK is less desirable than the flash point of the other examples using higher flash point ketones, and the addition of ketone tends to decrease the time required for initial strength, but increases the VOC. The specific ester of dicarboxylic acid with methanol (DBE-6) used can be as shown in Table 5 with NMP as the main solventOther esters of (a). The methylnaphthalene used in the experiment had a purity of > 95%. SS-150 is Sure Sol  and is 98% benzene C₁₀The isomer, SS-150ND, is similar to SS-150, but lacks naphthalene. SS-150 and SS-150ND as petroleum fractions were obtained from Koch specialty Chemicals group (Corpus Christi, Texas).

TABLE 6
											Examples	CPVC1Percent by weight of resin	Silicon oxide2% by weight	NMP weight percent	MNaph	SS-150% (by weight)	SS-150 ND% (heavy)	DBE-64% by weight	MEK% (by weight)	MIAK% (weight)	Weight percent of MIBK
707	13.51	1.5	50	-	-	-	27	8	-	-
											707A	13.51	1.5	58	-	-	-	27	-	-	-
707B	13.51	1.5	50	-	-	-	27	-	8	-
											707C	13.51	1.5	50	-	-	-	27	-	-	8
233	102	0	-	53	-	-	29	8	-	-
											234	102	0	-	53	-	-	29	-	10	-
235	102	0	-	53	-	-	29	-	-	10
											236	102	0	-	61	-	-	29	-	4	-
247	102	0	-	-	54	-	30	-	10	-
											248	82	0	-	-	54	-	30	-	-	8
250	82	0	-	-	-	54	30	-	10	-
											251	82	0	-	-	-	54	30	-	-	8

1.67.3% by weight Cl chlorinated polyvinyl chloride, and an inherent viscosity of 0.92.

2.67.0% by weight Cl chlorinated polyvinyl chloride, and an inherent viscosity of 0.68.

3. Fumed silica was obtained from Aldrich.

4. Dimethyl adipate available from Dupont under the trade name DBE-6

NMP is N-methyl-2-pyrrolidone, MEK is methyl ethyl ketone, MIAK is methyl isoamyl ketone, MIBK is methyl isobutyl ketone, and m-Naph is methylnaphthalene. Flash point of ketones according to Merck guide 10 th editionAt 24, 10 and 73F.

Table 6 (continue)
										Examples	VOC g/l5	Viscosity cp	Initial strength	Hydrostatic burst at 55/psi for 0.10 hr, 551psi	Hydrostatic failure of 4 hours, 403psi	Flash point of F	Hydrostatic fracture at DIA180 ℃ F2	Storage stability at 120 ° F30 days	Satisfies ASTM 493
707	172	1728	2	0.07 hour failure	3.92 hours failure	86	By passing	Failure of	Failure of
										707a	72	1662	3	By passing	By passing	203	By passing	Failure of	By passing
707b	97	1373	3	By passing	By passing	167	By passing	Failure of	By passing
										707c	73	1407	3	By passing	By passing	131	By passing	By passing	By passing
233	305	1218	3	-	-	77	By passing	By passing	-
										234	189	6753	3	By passing	By passing	167	By passing	By passing	By passing
235	229	8518	2	By passing	2.64 hours failure	131	By passing	By passing	Failure of
										236	128	1830	4	-	-	230	By passing	By passing	-
247	300	2880	2	By passing	By passing	149	By passing	By passing	By passing
										248	308	191	2	By passing	2.28 hours failure	122	By passing	By passing	Failure of
250	369	3790	1	By passing	By passing	140	By passing	By passing	By passing
										251	414	1300	2	-	-	122	By passing	By passing	-

VOC is volatile organic compounds determined by the SCAQMD316A method.

Measured by the method of ASTM D3828-87.

ASTM 493, see ASTM D1598-86 and D1599-88.

While the above examples of the present invention do not all pass all tests individually (e.g., examples 235 and 248 fail the 4 hour 403psi hydrostatic failure test), overall, the examples specify and suggest how to adjust the underrun characteristics to achieve the desired performance. Example 234 shows that the desired properties are obtained by replacing MIBK in example 235 with MIAK. A similar change is also demonstrated for example 247 compared to example 248. It is expected that other minor variations in the blending solvent (MIAK differing from MIBK by only one carbon atom per molecule) may also compensate for the insufficient characteristics, and the overall performance may be optimized by routine experimentation.

In summary, what has been described is a novel low VOC solvent based adhesive that has not been seen before, and a method of applying the low VOC solvent based adhesive to two thermoplastic materials to be bonded together. The adhesive preferably has a flash point in excess of 100 ° F (as measured by ASTM D3828-87). Although specific embodiments and examples are disclosed herein, it should be borne in mind that these embodiments and examples are provided to illustrate and describe the present invention and not to limit the invention. Of course, modifications made within the ordinary skill in the art are also considered to be within the scope of the present invention as defined by the following claims.

Claims (23)

1. A solvent-based adhesive comprising

a) From 38 to 75 weight percent of a first solvent which is at least one alkyl substituted naphthalene having one or more alkyl substituents and having from 11 to 14 carbon atoms or at least one alkyl substituted benzene having one or more alkyl substituents and having from 10 to 14 carbon atoms, or combinations thereof;

b) from 5 to 20% by weight of a thermoplastic resin; and

c) from 5 to 47% by weight of one or more auxiliary solvents selected from one or more of the following compounds:

-polycarboxylic acids having a total number of carbon atoms from 4 to 15;

-mono-or diesters of said polycarboxylic acids having a total number of carbon atoms of at most 19;

-said polycarboxylic acid alkyl ester acyl chloride having a total number of carbon atoms of at most 17;

-said polycarboxylic acid chloride having a total number of carbon atoms from 4 to 15;

a ketone having 3 to 15 carbon atoms;

-or combinations thereof, wherein the amount of volatilization of the one or more auxiliary solvents is controlled to maintain the solvent-based binder at a volatile organic content of less than 450g/l, as determined by method test 316A of air quality management on the south coast of the united states of america and wherein the weight percentages are based on the weight of the solvent-based binder.

2. A solvent-based adhesive according to claim 1, with the proviso that the total amount of said one or more auxiliary solvents that has any flash point below 37.8 ℃ (100 ° F) as determined by ASTM D3828-87 is less than 10% by weight and the volatile organic content is less than 350g/l as determined by test method 316A.

3. A solvent based adhesive according to claim 2, with the proviso that the total amount of said one or more solvents that have any flash point below 10 ℃ (50 ° F) is less than 5% by weight.

4. The solvent-based adhesive of claim 1, wherein said thermoplastic resin comprises polyvinyl chloride, chlorinated polyvinyl chloride, poly (acrylonitrile-butadiene-styrene), or polystyrene, and said first solvent is present in an amount of from 38% to 65% by weight.

5. A solvent based adhesive according to claim 4 wherein said thermoplastic resin is present in an amount of from 5 to 15% by weight.

6.A solvent based adhesive according to claim 4, wherein said adhesive comprises from 5 to 20% by weight chlorinated polyvinyl chloride.

7.A solvent based adhesive according to claim 1, wherein said at least one alkyl substituted naphthalene and/or alkyl substituted benzene is present in an amount of from 38 to 65% by weight.

8. The solvent-based adhesive of claim 7 wherein said volatile organic content is less than 350g/l as determined by test method 316A.

9. A solvent based adhesive according to claim 8 wherein said thermoplastic resin comprises from 5 to 20% by weight chlorinated polyvinyl chloride.

10. The solvent-based adhesive of claim 4 wherein said one or more auxiliary solvents comprise from 10 to 35 weight percent of one or more aliphatic polycarboxylic acids having a total of from 4 to 15 carbon atoms, mono-or diesters of said polycarboxylic acids having a total of from 4 to 19 carbon atoms, alkanoylchloride of said polycarboxylic acid having a total of from 4 to 17 carbon atoms, acid chloride of said polycarboxylic acid having a total of from 4 to 15 carbon atoms, or combinations thereof.

11. The solvent-based adhesive of claim 10 wherein said one or more co-solvents comprise from 25 to 35 weight percent of one or more mono-or diesters of said polycarboxylic acid and/or acid chlorides of said polycarboxylic acid, or combinations thereof.

12. The solvent-based adhesive according to any one of claims 1 to 11, wherein said auxiliary solvent is selected from the group consisting of pimelic acid, monomethyl glutarate, monomethyl pimelate, monomethyl azelate, monomethyl sebacate, monomethyl adipate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl pimelate, dimethyl suberate and dimethyl azelate, glutaryl chloride, adipoyl chloride and pimeloyl chloride, or mixtures thereof.

13. A solvent-based adhesive as claimed in claim 11, wherein said ketone is present in an amount of up to 15% by weight, based on the weight of said solvent-based adhesive.

14. A solvent-based adhesive according to claim 13, wherein said one or more ketones consist essentially of ketones having a flash point greater than 21.1 ℃ (70 ° F) as measured by ASTM D3828-87.

15. The solvent-based adhesive of claim 13, wherein the one or more ketones are selected from the group consisting of 5-methyl-2-hexanone and 4-methyl-2-pentanone, or combinations thereof.

16. A solvent based adhesive according to claim 13, wherein said adhesive comprises from 10 to 13.5% by weight chlorinated polyvinyl chloride.

17. A solvent based adhesive according to claim 16, wherein said at least one alkyl substituted naphthalene and/or alkyl substituted benzene is present in an amount of from 38 to 65% by weight.

18. The solvent-based adhesive of claim 10 wherein the volatile organic content is less than 350g/l as determined by test method 316A.

19. The solvent-based adhesive of claim 10 wherein the volatile organic content is less than 250g/l as determined by test method 316A.

20. A solvent-based adhesive comprising

a) From 38 to 70% by weight of at least one alkyl-substituted naphthalene having 11 to 14 carbon atoms and/or an alkyl-substituted benzene having at least one alkyl substituent and 10 to 14 carbon atoms;

b) from 5 to 20% by weight of chlorinated polyvinyl chloride; and

c) from 10 to 35% by weight of one or more

Polycarboxylic acids having a total number of carbon atoms of from 4 to 15

-mono-or diesters of said polycarboxylic acids having a total number of carbon atoms of at most 19

-said polycarboxylic acid alkyl ester acyl chloride having a total number of carbon atoms of at most 17

-said polycarboxylic acid chloride having a total number of carbon atoms of from 4 to 15, 15% by weight or less of one or more ketones having from 3 to 15 carbon atoms, or combinations thereof.

The binder has a volatile organic content of less than 450g/l as determined by test method 316A.

21. The solvent-based adhesive of claim 20 wherein the volatile organic content is less than 350g/l as determined by test method 316A.

22. The solvent-based adhesive of claim 21 wherein the volatile organic content is less than 250g/l as determined by test method 316A.

23. A solvent based adhesive according to claim 20, wherein said one or more ketones comprise from 5 to 10% by weight ketones having a flash point greater than 21.1 ℃ (70 ° F) as measured by ASTM D3828-87.