WO2009012545A1

WO2009012545A1 - Toluene-free balanced solutions of solvents for contact adhesives

Info

Publication number: WO2009012545A1
Application number: PCT/BR2008/000174
Authority: WO
Inventors: André Luis Conde DA SILVA; Carlos Roberto Tomassini; Fábio ROSA; Airton Antonio SÁBIO; Rovício Ubirajara MIGUEL
Original assignee: Oxiteno S.A. Indústria E Comércio
Priority date: 2007-07-26
Filing date: 2008-06-23
Publication date: 2009-01-29
Also published as: MX2010000756A; CL2008001548A1; BRPI0703285A2; AR067620A1; BRPI0703285B1

Abstract

The invention relates to balanced solutions of solvents without toluene for contact adhesives based on polychloroprene resins, basically consisting in a mixture of mutually miscible solvents, intended to promote the solubility of the above cited resins. Such solutions comprise in their formulation a range of organic compounds with distinct characteristics, such as aliphatic and/or cycloaliphatic hydrocarbons, esters based on the alkyl acetates, comprising alkyl groups with 4 to 6 carbon atoms, alcohols with straight or branched carbon chains with 2 to 6 carbon atoms and ketones with a structural composition comprised of 3 to 5 carbon atoms.

Description

"TOLUENE-FREE BALANCED SOLUTIONS OF SOLVENTS FOR CONTACT ADHESIVES"

Field of the invention The present invention refers to contact adhesives, particularly those that use in their composition a plurality of solvents of chemical functions, and more particularly those which composition is devoid of toluene or aromatic hydrocarbon derivatives.

Prior art

Contact adhesives are substances which purpose is to join different parts or materials, introducing new functions and properties that provide to the final assembly a value that is greater than the sum of its components alone, in addition to providing a significant reduction of the time and/or cost of assembly when compared with other production processes such as welding of metals, weaving of fabrics or yet the mechanical joining using rivets, screws and nails.

The extensive use of adhesives, glues and sealants in the automotive industry, aviation, paper, electric and electronics industries, furniture, leather and shoemaking and in civil construction entails a continuing demand of new formulations with better stability and better physical and mechanical properties. Such formulation is aimed at providing a competitive end product, however less toxic than the prior art formulations, moisture-resistant and having an excellent cost/benefit ratio, among other properties.

Among the wide variety of existing contact adhesives there should be pointed out those that incorporate in their formulation the polymer polychloroprene (CR), due to the same improving the various characteristics of the articles produced thereby. The said improvement is achieved due to the fact that the said polymer evidences high resistance to weather exposure and non-polar products, in addition to constituting a thermoplastic product with weak mechanical properties prior to vulcanization, and thermo-rigid, adherent to metals and resistant to aging, chemical agents and flame after being vulcanized. Furthermore, it is obtained by polymerization of the monomer chloroprene, and differently from the other elastomers, it can be vulcanized with magnesium oxide, in addition to being resistant to chemical attack, particularly to seawater, due to its formulation including chlorine atoms.

Furthermore, it evidences a strong tendency to crystallize and to form crystals in the macromolecule, which occurs in the form of a more or less strong hardening during the conservation of the rubber, of the raw mixture, or of the vulcanized product at ambient temperature, and particularly at low temperatures. Such tendency is stronger in rubbers whose structures were not subject to modification, and may be weakened with the introduction of plasticizers or resins of an adequate nature.

Crystallization is a property that is inherent to polychloroprene rubbers, although some crystallize faster than others. As it develops, there occurs a small reduction in volume, however without occurrence of crystallization at locations with high temperatures, since the orientation forces are dominated by the vigorous molecular motion.

The structure of the said polymer may be modified by means of copolymerization of the chloroprene with sulfur and/or butadiene, aiming to provide a family of the materials evidencing improved and increased chemical and physical properties. To that end, the polychloroprene rubber was split into two distinct groups, to wit: those intended for the manufacture of adhesives and those intended for general industrial application, this latter being characterized by being split into three families: type G family, type W family and type T family.

Within the type G family, the most typical grades of GN neoprene are those whose stability is limited as a raw material, while the GNA and GT neoprenes evidence a better resistance to crystallization, although still weak.

The neoprenes of the W family, in addition to evidencing a better storage stability, are more resistant to crystallization, due to the modification with mercaptan undergone thereby during production. Furthermore, they have a more uniform distribution of molecular weight and usually require organic accelerators in order to achieve a reasonably fast vulcanization. The most typical grades of the W family are the neoprenes W, WHV, WK and WRT, this latter being characterized by being more resistant to crystallization.

Similarly to the W type family, the type T family of neoprenes, which subdivides in to the TW and TRT neoprenes, have a gel polymer moiety aimed at improving their behavior, are resistant to crystallization and require organic accelerators, in addition to having low nerve and shrinkage.

Presently the contact adhesive formulations incorporate a large amount of toluene, see for example the disclosure of document No. PI0501666-5, which, due to a certain amount of toxicity and rapid evaporation, entails damage to the nervous system, entailing short-term or long-term effects ranging from tiredness, nausea, mental confusion, weakness, loss of memory, loss of appetite, hearing and vision, and might even cause loss of consciousness and death.

Due to their toxic properties and the fact that they are commercialized without restrictions, such adhesives are used as hallucinogenic substances, a fact that causes a proliferation of chemical substances abusers, thereby increasing the rates of criminal events and death by intoxication. Such fact may be explained in that the applicability in question derives from direct contact with the product.

There also exist contact adhesive formulations prepared based on the solvent cyclohexane, see for example the disclosure of document No. PI 9901812-8, however still implying limitations in terms of their toxic properties, environmental issues, performance and cost-benefit ratio.

Objects of the invention

In light of what has been set forth above, the object of the present invention consists in the provision of a composition of solvents with various chemical functions, however devoid of the organic compound toluene or aromatic hydrocarbon derivatives.

One other object of the invention is to provide the solubility of the neoprene or polychloroprene polymers.

One further object of the invention consists in the provision of a solution with less ozone formation potential at low atmospheric levels.

Yet another object of the invention consists in the provision of a formulation comprehending not only an excellent performance but also an excellent cost/benefit ratio.

Another object of the invention consists in the provision of a formulation having characteristics similar to those of a formulation which composition comprises toluene.

Brief description of the invention

The above listed objects, as well as others, are achieved by the invention by means of the provision of balanced solvent solutions comprising a plurality of hydrocarbons, alkyl acetates, alcohols and ketones, within the scope of providing the solubilization of the polychloroprene resins.

According to one other characteristic of the invention, the said solutions comprise, among a range of organic compounds, 2-butanone, 1- methylpropanol, aliphatic and cycloaliphatic hydrocarbons and acetates.

According to one further characteristic of the invention, the alkyl group comprises a carbon chain varying between 2 and 6 carbon atoms.

According to yet another characteristic of the invention, the ketone group has a variance of between 3 and 5 carbon atoms.

Detailed description of the invention

The present invention is based on the fact that the total or partial absence of the toluene or of the aromatic hydrocarbon derivative compounds provides as a result a solution for contact adhesives which toxicity level is substantially lesser that in formulations containing toluene. The said solution is based on the use of mutually miscible solvents, and is prepared by mixing a plurality of organic solvents through a range of systems for the purpose of providing its homogenization as a product and to solubilize the polychloroprene resins that constitute the contact adhesives.

From the physical-chemical perspective, and taking into consideration the ample variety of possible formulations, the said solubility will be achieved in the measure that the solutions themselves achieve an excellent performance regarding their applicability, density, viscosity and drying time, in order to fulfill the commercial requirements of the product being manipulated.

Regarding the composition of the said solutions, there are employed in the formulation thereof substances corresponding to four organic functions, to wit: hydrocarbons, esters, alcohols and ketones.

The hydrocarbons used in the mixture comprehend, in their entirety, both aliphatic and cycloaliphatic hydrocarbons, where the sum total thereof comprises about 10 to 50% in mass of the total ingredients.

As for the substances that comprise the organic function of esters, there are present therein, in a mass percentage level of 10 to 50%, the alkyl acetates having in the alkyl group an amount of carbon which variation ranges from 2 to 6 atoms. There is used the same percentage level for the substances formed by oxidation of the secondary alcohols, more specifically the ketones, however the said ketones evidence a structure comprising from 3 to 5 carbon atoms.

The alcohols employed in the formulation of the solutions have a straight or branched carbon chain comprised of a variation of carbon atoms in excess of 2 and of less than 6, in a concentration comprised between 5 and 30% in mass of the above cited substances.

For purposes of illustration of the substances that characterize the solutions, there may be cited, among a wide variety thereof, the n-hexane, n-heptane, methyl-cyclohexane, cyclohexane, acetates of ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, isopentyl, amyl and hexyl, ethanol, propanol, isopropanol, n-butanol, isobutanol, sec-butanol, pentanol, isopentanol, hexanol, propanone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, etc.

Due to the wide variety of embodiments of the invention, we might cite as examples for purposes of information and clarification on the compositions, some formulations based on 2-butanone, 1 -methyl propanol, aliphatic and cycloaliphatic hydrocarbons, 1 -methyl propyl acetate, 3 -methyl butyl acetate and butyl ethanoate, that provided the complete solubilization of the polychloroprene resin, without however such formulations restricting the scope of the invention.

FORMULATION 1

FORMULATION 2

FORMULATION 3

FORMULATION 4

FORMULATION 5

In one other embodiment of the invention which mass percentages encompass a wider range of levels, we may cite, as illustration, formulations comprising about 10 to 50% aliphatic and/or cycloaliphatic solvents, preferably based on the compounds which carbon chain has 6 to 10 atoms, about 10 to 50% ketones, preferably 2-butanone and/or propanone, alkyl acetates with a carbon chain comprised of 4 to 6 carbon atoms, preferably 3 -methyl butyl acetate and/or 3 -methyl propyl acetate and/or n- butyl acetate in a range comprised between 10 and 40% and the alcohols based preferably on 1 -methyl propanol, in a concentration of from 5 to 30%.

Claims

1. Toluene-free balanced solutions of solvents for contact adhesives based on polychloroprene resins comprising a plurality of miscible solvents having various chemical functions, which may comprise hydrocarbons, ketones, alcohols and esters, characterized in that the mixture comprises about 10 to 50% in mass of ketones with a carbon chain comprised of between 3 and 5 carbon atoms, about 10 to 50% in mass of aliphatic and cycloaliphatic hydrocarbons with a carbon chain comprised of 6 to 10 carbon atoms, about 5 to 30% in mass of alcohols with a carbon chain comprised of 2 to 6 carbon atoms and about 10 to 50% in mass of alkyl acetates with a carbon chain comprised of 4 to 6 carbon atoms in the alkyl group.

2. Balanced solutions of solvents, as claimed in claim 1, characterized in that the alkyl acetates are preferably isopentyl acetate and isomers thereof, and/or 3-methyl propyl acetate.

3. Balanced solutions of solvents, as claimed in claim 2, characterized in that the alkyl acetates comprise about 20 to 40% in mass of the mixture.

4. Balanced solutions of solvents, as claimed in claim 1, characterized in that the said alcohols are preferably isobutanol and/or sec- butanol and/or isopentanol.

5. Balanced solutions of solvents, as claimed in claim 4, characterized in that the alcohols comprise about 10 to 20% in mass of the mixture.

6. Balanced solutions of solvents, as claimed in claim 1, characterized in that the ketone is preferably 2-butanone.

7. Balanced solutions of solvents, as claimed in claim 6, characterized in that the said ketone comprises about 10 to 30% in mass of the mixture.

8. Balanced solutions of solvents, as claimed in claim 1, characterized in that the said aliphatic and cycloaliphatic hydrocarbons preferably have a carbon chain comprised of 6 to 8 carbon atoms.

9. Balanced solutions of solvents, as claimed in claim 8, characterized in that the aliphatic and cycloaliphatic hydrocarbons comprise about 20 to 40% in mass of the mixture.

10. Balanced solutions of solvents, as claimed in claims 1 to 9, characterized by being produced by means of any substance homogenizer system.

11. Balanced solutions of solvents, as claimed in claims 1 to 9, characterized in that the mixture of the organic compounds provides the solubility of the polychloroprene resins.