WO2017144929A1

WO2017144929A1 - Solvent system for thermoplastic adhesive formulation, method of solubilization thereof and use for bonding thermoplastic articles

Info

Publication number: WO2017144929A1
Application number: PCT/IB2016/000170
Authority: WO
Inventors: Fernanda Grigoletto; Sergio Martins; TOSTO Diana MARTINIAK
Original assignee: Rhodia Poliamida E Especialidades Ltda
Priority date: 2016-02-24
Filing date: 2016-02-24
Publication date: 2017-08-31

Abstract

The present invention generally relates to thermoplastic adhesives, and more particularly to adhesives used for bonding or joining PVC (polyvinyl chloride), CPVC (chlorinated polyvinyl chloride) or ABS (acrylonitrile butadiene styrene) pipes. More specifically, the present invention describes the use of a solvent system comprising glycerol ketals and/or acetals for solubilizing thermoplastic resins used in the application, notably in replacement of heterocyclic solvents (e. g., tetrahydrofuran or N-methyl pyrrolidone).

Description

SOLVENT SYSTEM FOR THERMOPLASTIC ADHESIVE FORMULATION, METHOD OF SOLUBILIZATION THEREOF AND USE FOR BONDING

THERMOPLASTIC ARTICLES TECHNICAL FIELD

The present invention generally relates to thermoplastic adhesives, and more particularly to adhesives used for bonding or joining PVC (polyvinyl chloride), CPVC (chlorinated polyvinyl chloride) or ABS (acrylonitrile butadiene styrene) pipes. More specifically, the present invention describes the use of a solvent system comprising glycerol ketals and/or acetals for solubilizing thermoplastic resins used in this application, notably in replacement of heterocyclic solvents (e. g., tetrahydrofuran or N-methyl pyrrolidone).

BACKGROUND ART

Solvent-based adhesives have been in use for joining thermoplastic pipes for years.

The development of these adhesives is largely responsible for growth of the thermoplastic pipe industry. Rapid-setting, solvent-based adhesives are used to bond the pipes together in a timely manner, as well as to bond thermoplastic pipe fittings (e.g. tees, ells, caps, couplings, and so forth) to such pipe. These rapid-setting, solvent-based adhesives allow for the testing and trouble-shooting of piping systems in a matter of hours while maintaining the long-term durability of pipe itself. These characteristics, 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 generally are formulated by dissolution of a relatively small amount of resin solids in a solvent carrier. The solvent-based adhesives work primarily by two means of action. First, upon surface application to a thermoplastic pipe surface, the solvent portion of the solvent-based adhesive formulation softens (i. e., partially dissolves) the outer surfaces of the pipe through solvation of the plastic such that the plastic surface becomes tackified. Subsequently, the adhesive "cures", i.e., hardens, by evaporation of the solvent fraction into the surrounding atmosphere from the pipe. Before the adhesive cures completely, the adhesive-treated plastic surface is brought into contact with the surface of another plastic piece to which it will be surface-attached, often under pressure. Secondly, the resin dissolved in the adhesive formulation remains at the plastic joint location and dries through the solvent evaporation and diffusion to ultimately provide a continuous joint between the bonded pipe surfaces, which aids in preserving the integrity of the entire pipe system.

The term "adhesive", as used in this specification and in the claims herein, whether in its singular or plural forms, includes cements, glues and pastes.

These solvent-based adhesives cure rapidly (viz., within a matter of hours), often permitting 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 integrity of the pipe itself. The resin solids component of the solvent-based adhesive can be selected so as to match the plastic pipe material and or plastic fitting material. This provides for a high degree of long-term durability for the piping system, often up to 30 to 40 years of useful life. This long service-life is essential for piping systems which are built into long-term structures such as homes and buildings, or where buried underground.

Thousands of miles of thermoplastic piping systems are constructed each day throughout the world, primarily by the means previously described. These systems are used in the transfer of potable water for drinking ; residential hot and cold water systems ; drain, waste, and vent (DWV) applications in home and industry ; turf and agricultural sprinkler systems ; Jacuzzi, spa and tub connections, residential and commercial fire sprinkler systems ; and so forth. These systems are crucial to the maintenance of safe and healthy means of transport of water and other chemicals throughout the world.

Evaporation of organic solvents from adhesives, as well as paints, coatings and the like, has created concerns from an environmental and health perspective, as it represents a source of air pollution and toxicity to humans. Typical solids (non-volatile) contents of thermoplastic solvent based pipe adhesives are up to 40% for PVC, with the balance of the formulation constituted primarily by solvent. Thus, current adhesives and primers incorporate the use of highly volatile solvents as major portions of the formulations. Among these, tetrahydrofuran (THF) is highly volatile at 20°C with a vapor pressure of 143 mm Hg. This solvent is prepared from 1,4-butanediol, use of which being also under discussion in many countries, notably to establish if this substance should be listed under the 1971 Convention on Psychotropic Substances. Co-solvents currently used are acetone (vapor pressure of 185 mm Hg), and methyl ethyl ketone (vapor pressure of 70 mm Hg).

Many of these solvents typically used in thermoplastic solvent-based pipe adhesives, e. g., tetrahydrofuran (THF), methyl ethyl ketone (MEK), and acetone, are considered to be volatile organic compounds ("VOC", calculated in accordance with ASTM D-2369). That is, VOCs are defined as volatile compounds which contain the element carbon, excluding compounds such as methane, carbon monoxide, carbon dioxide, carbonic acid, metallic carbides and carbonates, ammonium carbonates, as well as certain exempted solvents such as methylene chloride, acetone and 1, 1, 1-trichloroethane.

THF is a heterocyclic compound that is readily commercially available. THF is a very efficient solvent in CPVC and PVC adhesives because of its effective dissolution of CPVC and PVC resins and its relatively high vapor pressure that allows fast bond formation. As a consequence, adhesive formulations employing THF as a solvent yield pipe joints that are very strong even under hydrostatic pressure. Another heterocyclic compound, N-methyl pyrolidine (NMP), also has been used in conventional PVC adhesives as it effectively dissolves PVC and CPVC resins. However, NMP has a relatively low vapor pressure and, consequently, it normally must be used in combination with a higher vapor pressure solvent or solvents, such as THF, in order to develop effective bond strength in a reasonable period of time. However, specific environmental concerns recently have been raised regarding the high content levels of THF present in many current solvent-based adhesive formulations, such as plastic pipe formulations.

For these reasons, it would be highly desirable to develop thermoplastic (e.g. PVC, CPVC or ABS) adhesive formulations that completely omit heterocyclic solvents, or at least significantly limit the content of heterocyclic solvents, such as THF, while still meeting performance standards applicable to thermoplastic pipe.

Therefore, the present invention aims to propose an optimized solvent system for use to solubilize thermoplastic resins that are intended to be used in thermoplastic adhesive formulations.

One of the objects of the invention is to propose an alternative solvent system for replacing THF or NMP while keeping a fast and efficient solubilization. The thermoplastic formulation should also have the advantage of having low odor, adequate volatility, no toxicity, a good environmental profile (non VOC) and low cost. SUMMARY OF THE INVENTION

The invention thus relates to the use of a solvent system comprising at least one compound of formula I below:

wherein

Ri and R₂, independently from one another, are selected in the group consisting of: hydrogen or a linear or branched C1-C12 alkyl, a C4-C12 cycloalkyl or an aryl.

R₃ is H, a linear or branched alkyl, a cycloalkyl, a -C(=0)R₄ group, with R₄ being a linear or branched C1-C4 alkyl or a C5-C6 cycloalkyl or -(^RsO)n— F with R₅ being a linear or branched C1-C12 alkylene group and R₆ being H, a linear or branched C1-C12 alkyl or a C5-C6 cycloalkyl and n=l to 9, for solubilizing a thermoplastic resin.

The present invention also proposes a thermoplastic adhesive formulation comprising a thermoplastic resin and a solvent system comprising at least one compound of formula I below:

wherein Ri and R₂, independently from one another, are selected in the group consisting of: hydrogen or a linear or branched C1-C12 alkyl, a C4-C12 cycloalkyl or an aryl.

R₃ is H, a linear or branched alkyl, a cycloalkyl, a -C(=0)R₄ group, with R₄ being a linear or branched C1-C4 alkyl or a C5-C6 cycloalkyl or -(RsO)_n— R6 with R₅ being a linear or branched C1-C12 alkylene group and R₆ being H, a linear or branched C1-C12 alkyl or a C5-C6 cycloalkyl and n=l to 9.

In addition, the present invention relates to the use of the above defined thermoplastic resin for bonding thermoplastic articles such as pipes or other molded articles.

Still another object of this invention is a method for solubilizing a thermoplastic resin wherein in a first step the thermoplastic resin is mixed with a first solvent system comprising at least one compound of formula I as defined above, and in a second step the resulting mixture is mixed with a second solvent system.

Last, the present invention is about a solvent system consisting of:

5-20% by weight of at least one compound of formula I as defined above,

40-80% by weight of cyclohexanone, and

Up to 100% by weight of n-Butyl acetate.

DETAILED DESCRIPTION OF THE INVENTION

The present invention thus concerns the use of a solvent system comprising at least one compound of formula I below:

wherein

Ri and R₂, independently from one another, are selected in the group consisting of: hydrogen or a linear or branched C1-C12 alkyl, a C4-C12 cycloalkyl or an aryl. R₃ is H, a linear or branched alkyl, a cycloalkyl, a -C(=0)R₄ group, with R₄ being a linear or branched C1-C4 alkyl or a C5-C6 cycloalkyl or -(RsO)_n— R₆, with R₅ being a linear or branched C1-C12 alkylene group and R₆ being H, a linear or branched C1-C12 alkyl or a C5-C6 cycloalkyl and n=l to 9, for solubilizing a thermoplastic resin.

According to the invention, the thermoplastic resin is advantageously selected in the group consisting of: polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), and Acrylonitrile-butadiene-styrene (ABS). In one embodiment, Ri and R₂, independently from one another, are selected in the group consisting of: hydrogen, methyl, ethyl, isopropyl, n-propyl, isobutyl, n-butyl, tert-butyl, n- pentyl, cyclopentyl, cyclohexyl or phenyl.

In a preferred embodiment, Ri and R₂, independently from one another, are selected in the group consisting of: methyl, ethyl, isopropyl, n-propyl, isobutyl, n-butyl, tert-butyl, n-pentyl, cyclopentyl, cyclohexyl or phenyl.

Advantageously, in formula I above R₃ is H or a -C(=0)R₄ group, with R₄ being methyl, ethyl, isopropyl, n-propyl, isobutyl, n-butyl or tert-butyl, or -(RsO),,— R₆, with R₅ being -CH₂-, - (CH₂)₂-, -CH(CH₃)-, -(CH₂)₃-,-C(CH₃)₂-, -CH(CH(CH₃)₂)-, -(CH₂)₄- or -CH(C(CH₃)₃)- and R₆ being H, methyl, ethyl, isopropyl, n-propyl, isobutyl, n-butyl or tert-butyl and n=l to 3.

One preferred embodiment is when Ri and R₂ are methyl and R₃ is H. In this case, the compound is commercially available, for example under the name Augeo^® SL191 or Solketal. This compound can be synthesized by reaction between glycerol and acetone, under well- known classical conditions.

In another embodiment, Ri is methyl, R₂ is isobutyl and R₃ is H. In this case, the compound is commercially available, for example under the name Augeo^® Clean Plus. This compound can be synthesized by reaction between glycerol and methyl-isobutyl ketone, under well-known classical conditions. In a third embodiment, Ri is methyl, R₂ is phenyl and R₃ is H. In this case, the compound is commercially available, for example under the name Augeo^® Film HB. This compound can be synthesized by reaction between glycerol and acetophenone, under well-known classical conditions.

In a fourth embodiment, Ri is isopropyl and R₂ and R3 are H. In this case, the compound is 2- isobutyl-2-methyl-l,3-dioxolane-4-methanol. This compound can be synthetized by reaction between glycerol and isobutyraldehyde, under well-known classical conditions. Another possibility is to have R_x and R₂ are methyl and R₃ is a -C(=0)R₄ group, with R₄ being methyl. In this case, the compound is commercially available, for example under the name Augeo^® ACT. This compound can be synthesized by transesterification of Solketal with an alkyl acetate under well-known classical conditions. Still another possibility is to have R_x is 2-ethylhexyl and R₂ and R3 are H. In this case, the compound is (2-(heptan-3-yl)-l,3-dioxolan-4-yl)methanol. This compound can be synthetized by reaction between glycerol and 2-ethylhexanal, under well-known classical conditions. Glycerol can be obtained as a coproduct from biodiesel production during the transesterification of triglycerides.

Advantageously, the compound of formula I is chosen from the group comprising: 2,2- dimethyl-l,3-dioxolane-4-methanol, 2,2-diisobutyl-l,3-dioxolane-4-methanol, 2-isobutyl-2- methyl-l,3-dioxolane-4-methanol, 2-isopropyl-l,3-dioxolane-4-methanol, 2-butyl-2-ethyl- l,3-dioxolane-4-methanol, 2-phenyl-l,3-dioxolane-4-methanol and 2-methyl-2-phenyl-l,3- dioxolane-4-methanol, 2,2-dimethyl-l,3-dioxolane-4-acetate, (2-(heptan-3-yl)-l,3-dioxolan- 4-yl)methanol and mixtures thereof. In one embodiment of the invention, at least two, more preferably two or three, compounds of formula I can be used as blend of solvents in the solvent system. As preferable examples of such blends include a blend of 2,2-dimethyl-l,3-dioxolane-4- methanol and at least a glycerol ketal and/or acetal chosen from the following group: 2,2- diisobutyl-l,3-dioxolane-4-methanol, 2-isobutyl-2-methyl-l,3-dioxolane-4-methanol, 2- isopropyl-l,3-dioxolane-4-methanol, 2-butyl-2-ethyl-l,3-dioxolane-4-methanol, 2-phenyl- l,3-dioxolane-4-methanol, 2-methyl-2-phenyl-l,3-dioxolane-4-methanol, 2,2-dimethyl-l,3- dioxolane-4-acetate, (2-(heptan-3-yl)-l,3-dioxolan-4-yl)methanol and mixtures thereof.

Apart from the compound of formula I above, the solvent system advantageously further comprises a ketone, preferably selected in the group consisting of: cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, acetone, butanone and mixtures thereof, more preferably cyclohexanone.

Also, the solvent system can further comprise an ester of C1-C4 carboxylic acid with a C1-C6 alcohol, preferably selected in the group consisting of: n-Butyl acetate, n-propyl acetate, methyl acetate, ethyl acetate, isobutyl acetate and mixtures thereof, more preferably n- Butyl acetate.

In a preferred embodiment, the solvent system is a blend consisting of least one compound of formula I as defined above, cyclohexanone and n-Butyl acetate. More preferably, the solvent system is a blend consisting of:

5-20%, preferably 5-10% by weight of at least one compound of formula I as defined above,

40-80%, preferably 50-70% by weight of cyclohexanone, and

- Up to 100% by weight of n-Butyl acetate.

In the most preferred solvent system according to the invention, the compound of formula I is 2,2-dimethyl-l,3-dioxolane-4-methanol.

The use according to the invention promotes the solubilization of the thermoplastic resin, notably it is equivalent to a thermoplastic adhesive formulation containing THF instead of one glycerol ketal and/or acetal of formula I. The present invention also concerns a thermoplastic adhesive formulation comprising at least one glycerol ketal and/or acetal of formula I described above. All the preferred embodiments detailed before, taken alone or in combination are also applicable to the thermoplastic adhesive formulation.

As explained above, the thermoplastic resin is advantageously selected in the group consisting of: polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), and Acrylonitrile-butadiene-styrene (ABS). The thermoplastic adhesive formulation according to the invention advantageously comprises from 5 to 50% by weight of, preferably 10 to 40% by weight of thermoplastic resin based on the total weight of the thermoplastic adhesive formulation.

The thermoplastic adhesive formulation of the invention may generally further comprise further additives like dispersants, anti-corrosion agents, biocides, thickeners, anti-foam agents and others. The total amount of further additives generally remains below 15% by weight of the thermoplastic adhesive formulation.

The present invention is also directed to the use of the thermoplastic resin described below, for bonding thermoplastic articles such as pipes or other molded articles.

A method for solubilizing a thermoplastic resin I also provided. As explained above, in a first step the thermoplastic resin is mixed with a first solvent system comprising at least one compound of formula I as defined above, and in a second step the resulting mixture is mixed with a second solvent system advantageously comprising a ketone and an ester, more preferably consisting of a ketone and an ester.

The ketone of the second solvent system is preferably selected in the group consisting of: cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, acetone, butanone and mixtures thereof, more preferably acetone. The ester of the second solvent system is preferably an ester of C1-C4 carboxylic acid with a C1-C6 alcohol, preferably selected in the group consisting of: n-Butyl acetate, n-propyl acetate, methyl acetate, ethyl acetate, isobutyl acetate and mixtures thereof, more preferably ethyl acetate.

In this method, the thermoplastic resin is also advantageously selected in the group consisting of: polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), and

Acrylonitrile-butadiene-styrene (ABS).

Conditions of solubilization first step

At this first step, advantageously from 5 and 50%, preferably from 20 and 40% and more preferably about 30%of thermoplastic resin is added to from 50 to 95%, preferably from 60 and 80% and more preferably about 70% of solvent system according to the invention.

The first step can be performed using an agitator, preferably under low agitation (generally from 100 to 400rpm, preferably about 200rpm).

Temperature is this first step can be set between 10 and 40°C, preferably room temperature, and at atmospheric pressure.

The resulting mixture is kept under those conditions during sufficient time to obtain solubilization, generally approximatively 2 hours. Conditions of solubilization second step

The second step is a step of viscosity adjustment. In this step, from 10 to 90%, preferably from 30 to 70% and more preferably about 50% of the resulting mixture from the first step is mixed with from 10 to 90%, preferably from 30 to 70% and more preferably about 50% of second solvent system comprising acetone and ethyl acetate.

The conditions of agitation, temperature and time of second step are similar to the ones of first step. The can be equal.

The second solvent system used in the method according to the invention is preferably a blend consisting of 40-60% by weight of acetone and 60-40% by weight of ethyl acetate.

Last, another object of the invention is a solvent system consisting of: 5-20%, preferably 5-10% by weight of at least one compound of formula I as defined above, preferably 2,2-dimethyl-l,3-dioxolane-4-methanol.

40-80%, preferably 50-70% by weight of cyclohexanone, and

Up to 100% by weight of n-Butyl acetate.

It has been demonstrated through the experimental part of the specification that said solvent system allows the solubilization of thermoplastic resins such as PVC resin.

Specific language is used in the description so as to facilitate the understanding of the principle of the invention. It should, however, be understood that no limitation of the scope of the invention is envisaged by the use of this specific language. Modifications, improvements and perfections may especially be envisaged by a person skilled in the technical field concerned, on the basis of his own general knowledge.

The present invention provides advantages over existing solvent systems for thermoplastic resin based adhesives. The invention proposes a solvent system including a green solvent, which has a good performance to solubilize the thermoplastic resin without causing injury to health contrary to THF and all BDO derivatives in general. This formulation has advantageously low toxicity, low odor and good environmental profile, and simultaneously exhibit high solvency for thermoplastic resins comparable to THF/NMP solvents.

Other details or advantages of the invention will become more clearly apparent in the light of the examples given below.

EXAMPLE

Methods of measure

For the example below, the solubilization of the thermoplastic resin has been measured after 2 hours under stirring, through visual observation of the solution.

In addition, viscosity has been measured at 25°C using a Brookfield viscosimeter.

Tests and results

A first solvent system (SSI) comprising 7.5% by weight of 2,2-dimethyl-l,3-dioxolane-4- methanol manufactured and sold by Solvay under the tradename Augeo SL191, 65% by weight of cyclohexanone and up to 100% of nButyl acetate manufactured and sold by Solvay, is prepared by simply mixing the components in a vessel.

A second solvent system (SS2) made of 60% by weight of acetone and 40% by weight of ethyl acetate, both manufactured and sold by Solvay is also prepared in a separate vessel.

Ex l

30g of CPVC resin (commercially available) are solubilized in 70g of the first solvent system under stirring, during 2 hours at 25°C, the resulting mixture is a 30% by weight concentrated CPVC solution in the first solvent system (SSI).

The visual observation shows a slightly white solution with no apparent residual solid resin.

Ex 1 comparative

As comparative example, 30g of CPVC resin (commercially available) are dissolved in 70g of THF (commercially available) under stirring, during 2 hours at 25°C, the resulting mixture is a 30% by weight concentrated PVC solution in THF.

The visual observation shows a clear and with high viscosity solution with no apparent residual solid resin.

Ex 2: Viscosity adjustment

To 50% by weight of the solutions obtained in example 1 and in comparative example 1, 50% by weight of either SS2 or MEK (commercially available) are added in order to adjust the viscosity. The results are indicated in table I below.

Table I

*Due to very high viscosity, it was not possible to measure it with the equipment being used Conclusion

The above results show that the use of SSI in replacement of THF give a final solution with lower viscosity, as it was possible to measure it at the equipment used. This shows better solubilization from this solvent system when compared to THF. Both MEK and SS2 were able to adjust the viscosity of final solution with very similar performance.

Claims

1. Use of a solvent system comprisin at least one compound of formula I below:

wherein

R₃ is H, a linear or branched alkyl, a cycloalkyl, a -C(=0)R₄ group, with R₄ being a linear or branched C1-C4 alkyl or a C5-C6 cycloalkyl or -(R₅0)_n— R₆, with R₅ being a linear or branched C1-C12 alkylene group and R₆ being H, a linear or branched C1-C12 alkyl or a C5-C6 cycloalkyl and n=l to 9, for solubilizing a thermoplastic resin.

2. Use according to claim 1, wherein Ri and R₂, independently from one another, are selected in the group consisting of: hydrogen, methyl, ethyl, isopropyl, n-propyl, isobutyl, n- butyl, tert-butyl, n-pentyl, cyclopentyl, cyclohexyl or phenyl.

3. Use according to claim 1 or 2, wherein R₃ is H or a -C(=0)R group, with R₄ being methyl, ethyl, isopropyl, n-propyl, isobutyl, n-butyl or tert-butyl or -(RsO)_n— 6, with R₅ being -CH₂-, -(CH₂)₂-, -CH(CH₃)-, -(CH₂)₃-,-C(CH₃)₂-, -CH(CH(CH₃)₂)-, -(CH₂)₄- or -CH(C(CH₃)₃)- and R₆ being H, methyl, ethyl, isopropyl, n-propyl, isobutyl, n-butyl or tert-butyl and n=l to 3.

4. Use according to claim 1 to 3, wherein the compound of formula I is selected in the group consisting of: 2,2-dimethyl-l,3-dioxolane-4-methanol, 2,2-diisobutyl-l,3-dioxolane-4- methanol, 2-isobutyl-2-methyl-l,3-dioxolane-4-methanol, 2-isopropyl-l,3-dioxolane-4- methanol, 2-butyl-2-ethyl-l,3-dioxolane-4-methanol, 2-phenyl-l,3-dioxolane-4-methanol and 2-methyl-2-phenyl-l,3-dioxolane-4-methanol, 2,2-dimethyl-l,3-dioxolane-4-acetate, (2- (heptan-3-yl)-l,3-dioxolan-4-yl)methanol and mixtures thereof.

5. Use according to claim 1 to 4, wherein at least two, more preferably two or three compounds of formula I are used in the solvent system.

6. Use according to anyone of claims 1 to 5, wherein the thermoplastic resin is selected in the group consisting of: polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), and Acrylonitrile-butadiene-styrene (ABS).

7. Use according to anyone of claims 1 to 6, wherein the solvent system further comprises a ketone, preferably selected in the group consisting of: cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, acetone, butanone and mixtures thereof, more preferably cyclohexanone.

8. Use according to anyone of claims 1 to 7, wherein the solvent system further comprises an ester of C1-C4 carboxylic acid with a C1-C6 alcohol, preferably selected in the group consisting of: n-Butyl acetate, n-propyl acetate, n-methyl acetate, ethyl acetate, isobutyl acetate and mixtures thereof, more preferably n-Butyl acetate.

9. Use according to anyone of claims 1 to 8, wherein the solvent system is a blend consisting of least one compound of formula I as defined in anyone of claims 1 to 5, cyclohexanone and n-Butyl acetate.

10. Use according to anyone of claims 1 to 9, wherein the solvent system is a blend consisting of:

- 5-20% by weight of at least one compound of formula I as defined in anyone of claims 1 to 5

- 40-80% by weight of cyclohexanone, and

- Up to 100% by weight of n-Butyl acetate.

11. Use according to claim 10, wherein the compound of formula I is 2,2-dimethyl-l,3- dioxolane-4-methanol.

12. Thermoplastic adhesive formulation comprising a thermoplastic resin and a solvent system comprising at least one compound of formula I below:

wherein

R₃ is H, a linear or branched alkyl, a cycloalkyl, a -C(=0)R₄ group, with R₄ being a linear or branched C1-C4 alkyl or a C5-C6 cycloalkyl or -(RsO)n— R6, with R₅ being a linear or branched C1-C12 alkylene group and R₆ being H, a linear or branched C1-C12 alkyl or a C5-C6 cycloalkyl and n=l to 9.

13. Thermoplastic adhesive formulation according to claim 12, wherein the at least one compound of formula I is as defined in anyone of claims 2 to 5.

14. Thermoplastic adhesive formulation according to any one of claim 12 or 13, wherein the thermoplastic resin is selected in the group consisting of: polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), and Acrylonitrile-butadiene-styrene (ABS).

15. Thermoplastic adhesive formulation according to anyone of claims 12 to 14, wherein the solvent system further comprises a ketone, preferably selected in the group consisting of: cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, acetone, butanone and mixtures thereof, more preferably cyclohexanone.

16. Thermoplastic adhesive formulation according to anyone of claims 12 to 15, wherein the solvent system further comprises an ester ofd-C4 carboxylic acid with a C1-C6 alcohol, preferably selected in the group consisting of: n-Butyl acetate, n-propyl acetate, methyl acetate, ethyl acetate, isobutyl acetate and mixtures thereof, more preferably n-Butyl acetate.

17. Thermoplastic adhesive formulation according to anyone of claims 1 to 16, wherein the solvent system is a blend consisting of a least one compound of formula I as defined in anyone of claims 2 to 5, cyclohexanone and n-Butyl acetate.

18. Thermoplastic adhesive formulation according to anyone of claim 12 to 17, wherein the solvent system is a blend consisting of:

5-20% by weight of at least one compound of formula I as defined in anyone of claims 1 to 5,

- 40-80% by weight of cyclohexanone, and

- Up to 100% by weight of n-Butyl acetate.

19. Thermoplastic adhesive formulation according to anyone of claims 12 to 18, wherein the thermoplastic resin represents from 5 to 50%, preferably 10 to 40% by weight of the total weight of the adhesive formulation.

20. Thermoplastic adhesive formulation according to anyone of claims 12 to 19, wherein the compound of formula I is 2,2-dimethyl-l,3-dioxolane-4-methanol.

21. Use of the thermoplastic resin according to anyone of claims 12 to 20, for bonding thermoplastic articles such as pipes or other molded articles.

22. Method for solubilizing a thermoplastic resin wherein in a first step the thermoplastic resin is mixed with a first solvent system comprising at least one compound of formula I as defined in anyone of claims 1 to 5, and in a second step the resulting mixture is mixed with a second solvent system comprising a ketone and an ester.

23. Method according to claim 22, wherein the thermoplastic resin is selected in the group consisting of: polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), and Acrylonitrile-butadiene-styrene (ABS).

24. Method according to anyone of claims 22 or 23, wherein the second solvent system consists of acetone and ethyl acetate, preferably 40-60% by weight of acetone and 60-40% by weight of ethyl acetate.

25. Solvent system consisting of:

40-80% by weight of cyclohexanone, and

Up to 100% by weight of n-Butyl acetate.

26. Solvent system according to claim 25, wherein the compound of formula I is 2,2- dimethyl-l,3-dioxolane-4-methanol.