CA2003986A1

CA2003986A1 - Process and composition for depositing a temporary barrier layer on spray booths and the like

Info

Publication number: CA2003986A1
Application number: CA002003986A
Authority: CA
Inventors: Ludwig Schieferstein; Juergen Geke; Joachim Conradi; Dieter Meyer
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 1988-11-26
Filing date: 1989-11-27
Publication date: 1990-05-26
Also published as: WO1990006344A1; EP0371378B1; ES2040967T3; EP0371378A1; EP0445216A1; JPH04502026A; ATE89305T1; DE58904345D1; DE3839935A1; BR8907790A; KR900701939A

Abstract

ABSTRACT OF THE DISCLOSURE
Spray booth walls and like surfaces subject to accumu-lations of waste solids can be protected by a subsequently removable barrier layer coating deposited from an aqueous solution of one water soluble copolymers of:
(A) from 15% to 90% by weight (calculated with ref-erence to the copolymer) of at least one nitrogen-free ole-finic monomer, and (B) from 85% to 10% by weight (calculated with ref-erence to the copolymer) of at least one linearly polymer-izable monomer containing at least one tertiary amine func-tion.
The copolymers preferably are at least partially neu-tralized with acid and/or quaternized, so that the pH of the total composition is not greater than 7.

Description

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PATENT
~ Docket D 8423 :
- P~OCESS AND ~OMPOSI~ION FOR DEPOSlTI~G A
TENPORARY B~RRIER LAYER O~ BPRAY BOOT~S ~N~ THE LIXE
' '-' BACKGROUND OF THE INVENTION
Field of the Invention The invention relates to a process and composition for depositing a temporary, subsequently removable barrier layer upon parts of spray-coating booths and like surfaces - liable to suffer undesirable accumulation of solids, prior to the start of a new spray coating or other working cycle, and concerns in particular the use for this purpose of aqueous compositions including polymers containing tertiary amino and/or quaternary ammonium groups.
statement of the Related Art The purpose of providing a temporary barrier layer over the internal walls of a paint spray booth beforQ an ensuing work cycle is to make it readily possible, by dis-solving away the intermediate barrier layer, afterwards to remove the encrusted paint layer formed on the walls of the booth from overspray during the work cycle. The desirabil-ity of such a procedure is already recognized. The consid-erations affecting the design of spray booths, from the viewpoint of plant manufacturers, have been described by R.S. Nickerson and B. Piel, (cf. Ann. Tech. Conf. Proc., Am. Electroplaters' Soc., 73rd Sess. Section A, Paper A2).
So-called temporary spray booth coatings of surfactant-con-taining poly(vinyl pyrrolidone), saccharide, and plasticiz-er mixtures are known from U.S. Patent 4,548,967 of Oct.
` 22, 1985 to Brown et al. Hot-water-soluble temporary spray booth coatings of surfactant-containing terpene hydrocarbon mixtures are known from U. S. Patent 3,476,575 of Nov. 4, 1969 to Arnold.
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, . 1 Z0[)39~36 DESCRIPTION OF THE INVENTION
It is an object of the present invention to provide a process and a composition, both based on the use of a particular type of copolymer, which, from an aqueous based r 5 composition in which it is homogeneously distributed, will deposit a continuous, flexible, protective film or barrier layer, having little sensitivity to humidity in the air, yet which can when desired be easily removed again by li-quid water.
The copolymers, whose use to form a temporary, subse-quently removable protective film or barrier layer in paint spray booths or like installations characterizes both the process and the composition of this invention, are inher-ently water soluble and/or predominantly or completely solubilized amino-containing copolymers that can be pre-pared by copolymerization of:
(A) 15 to 90 % by weight (calculated with reference to the copolymer) of at least one nitrogen-free ole~inic monomer;
and (B) from ~5~ to 10% by weight (calculated with refer-ence to the copolymer) of at least one linearly polymeriz-able monomer containing at least one tertiary amine func-tional group. These copolymers may be used as such, as salts obtainable by partially or completely neutralizing the amine functional groups in the copolymers with acid, and/or as derivatives made by quaternizing the amine func-tional groups. At least half, preferably at least 75 %, and more preferably at least 90 ~ of the total mass of the - copolymer used should be soluble in water. To the extent that it is needed or desired to achieve some particular concentration, solubilization can be effected by completely or partially neutralizing the amino groups of the copoly-- mers with acid and/or by completely or partially quaterni~-ing them.
: It may here be noted that some of the amino-containing copolymers used according to this invention are known per se, as coating material for tablets, from DE-A 2 135 073, the relevant content of which is incorporated herein by -` Z 01039~6 ~-reference, to the extent not inconsistent with any express .^; statement herein.
Illustrative but typical examples of nitrogen-free olefinic monomers suitable as part of component (A) in the - 5 amino-containing copolymers used according to the inven-tion, are, for instance: alpha,beta-unsaturated mono- and dicarboxylic acids, particularly acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumar-ic acid, and esters of the aforesaid acids, e.g. acrylic acid alkyl esters, methacrylic acid alkyl esters, hydroxy-ethyl-acrylate and -methacrylate, beta-hydroxypropyl ac-rylate and -methacrylate, beta-hydroxybutyl-acrylate and -methacrylate, gamma-hydroxybutylacrylate and -methacryl-ate, glycerol mono-acrylate and -methacrylate, ethylene glycol mono-acrylate an~ -methacrylate; also vinyl esters, particularly vinyl acetate, and vinyl ethers as well as styrene (optionally mixed with butadiene)l alpha-methylsty-rene, vinyl toluene and the like. Particularly pre~erred nitrogen-free olefinic monomers for use in component (A) are esters of acrylic or methacrylic acid with C1 to C4-mon-oalcohols, e.g. the methyl, ethyl, propyl and butyl esters of these acids, optionally mixed with excess acrylic and/or methacrylic acid. The aforementioned nitrogen-free ole-finic monomers can be used either individually or in admix-ture with others as copolymer components.
The linearly-polymPrizable monomers containing at least one tertiary amine function used according to the invention in component (B) are already known per se to one skilled in the polymer art, and illustrative suitable ex-amples thereof are: the dialkyl amino alkyl esters of - acrylic, methacrylic, maleic, itaconic, and fumaric acids.
Particularly preferred for use in component ~B) are esters of acrylic or methacrylic acid with monoalcohols, particu-larly C2 to C6 monoalcohols, that have a tertiary amine function, such as dimethylamino ethyl-acrylate and -methacrylate, diethylamino ethyl-acrylate and -methacryl-ate, dipropylamino ethyl-acrylate and -methacrylate, ZOC)39~
dibutylamino ethyl-acrylate and -methacrylate, 2-(dimethyl-amino) propyl-acrylate and -methacrylate, 2-~diethylamino) propyl-acrylate and -methacrylate, 2-(diethylamino) butyl-acrylate and -methacrylate, dimethylamino neopentyl--acrylate and -methacrylate, diethylamino neopentyl-acrylate and -methacrylate, and the like. Other suitable linear-ly-polymerizable monomers containing a tertiary amino func-tion are for instance 2-vinyl pyridine and 4-vinyl pyri-dine, as well as N-substituted diallyl amines. The afore-mentioned linearly polymerizable monomers can be used eith-er individually or in admixture with others as copolymer components.
The choice of the monomers in (A) and ( B) and the proportions in which they are to be used in order to obtain the desired clear aqueous compositions can be readily de-termined by one skilled in the polymer art. For example, where there are smaller amounts, e.g. less than 20~ by weight, of the linearly-polymerizable monomers containing tertiary amino functions (B), one will select nitrogen-free monomers (A) which are at least partially water soluble.
An example of such a partially water soluble co-monomer is the methyl ester of acrylic acid (methyl acrylate). The selection of monomers to produce completely water soluble co-polymers is also known to one of ordinary skill in poly-mer science.
- In a preferred embodiment of the invention the copol-ymers containing amino groups have glass transition temper-atures ~Tg) in the range from -30 to +50~ C. Adjustment of the copolymer to an appropriate glass transition tempera-ture by selecting suitable co-monomer mixtures and/or poly-!, merization conditions is within the ordinary skill of the polymer art.
In the aqueous compositions according to the inven-tionl the amino group containing copolymers are preferably present in an amount of from 5% to 75% by weight, and more preferably from 15% to 50% by weight (calculated with ref-erence to the total weight of the composition). For immed-. ~

- 2~039~

iate application these compositions can also be further diluted, to very low concentrations. In the coating of spray booths the desired layer thickness determines the concentration of the copolymers in the aqueous composition.
This can be as low as 1% by weight, calculated with refer-ence to the total weight of the composition.
The preferred clear aqueous compositions can be ob-kained by neutralizing the copolymers, i.e. neutralizing their amino groups. This may be achieved by adding to an aqueous dispersion of the copolymers just sufficient acid for a clear composition to be obtained. The amount of acid necessary for this naturally depends on the nature and com-position of the copolymer - a clear phase is generally established when the amino function is still only partially neutralized, but it is obviously also possible completely to neutralize the amino function. The acids employed for neutralization should of course be physiologically harm-less, but aside from that, any of the common inorganic and organic acids are suitable, such as sulfuric acid, hydro-chloric acid, phosphoric acid, formic acid, and acetic acid. However, phosphoric acid, formic acid, and acetic acid are particularly preferred.
Instead of neutralizing with acids as just described, it is also possible to quaternize the amino groups of the copolymers. For this purpose conventional alkylating agents, preferably methyl iodide, may be used.
The compositions of th~ invention preferably contain from 5% to 75% by weight, calculated with reference to the total weight~ of the previously defined copolymers contain-- 30 ing amino groups. However, it is particularly preferred that the compositions contain from 15% to 50% by weight, with reference to the total composition weight, of such copolymers.
In a particularly preferred embodiment, the present invention relates to a~ueous compositions for coating spray booths, containing in particular from 15 % to 50 % by weight, calculated with reference to the total weight of 2~ 398~

the composition, of copolymers containing amino groups, obtained by the copolymerization of: (A) ~rom 15~ to less than 70% by weight (calculated with reference to the copol-ymer) of nitrogen-free olefinic molecules; and (B) from 85%
to more than 30~ by weight (calculated with reference to the copolymer) of linearly polymerizable molecules contain-ing at least one tertiary amine function, and in which the amine groups of the copolymers may be completely or par-tially neutralized or quaternized.
It is preferred that the copolymers be completely or partially neutralized or quaternized, so as to produce a composition with a pH value of 7 or less. Most preferably, neutralization is accomplished using phosphoric acid. This neutralization gives the aqueous compositions a strongly anti-corrosive effect.
Further preferred features of the aqueous compositions of the invention have already been explained above.
It may be desirable to adjust the viscosity of the compositions according to the invention to as low a value as possible. For this purpose several possibilities are available to one skilled in the art. It is, for example, possible to add small amounts of viscosity regulators dur-ing the synthesis of the copolymers. Suitable viscosity ; regulators are thioglycolic acid and mercapto ethanol, as 2S well as the many known ionic cross-linking agents, such as polyfunctional carboxylic acids, for example dicarboxylic acids with from 2 to 10 carbon atoms. It should be borne in, mind however, that high amounts OI regulators can im-pair adhesiveness and, generally speaking therefore, the proportion of regulators should not exceed 2%. In many cases additions of 0.5 or 0.1 % and sometimes even smaller amounts are sufficient to reduce the viscosity.
The aqueous compositions of the invention can also when desired contain any of the usual additives, such as preservatives, colorants, and the like.
The production of aqueous compositions according to the invention can be carried out using known methods, '`

Z~3039~6 - within the ordinary sklll o~ the art. For general guid-ance, it is advisable to ensure that the molecular weight of the copolymers is not less than lO,OOQ, and preferably not less than 30,000, because otherwise the adhesive prop-erties of the barrier layer may be impaired. Synthesis of the copolymers may be conveniently carried out, for ex-ample, by polymerization in aqueous solution before or after the addition of the neutralizing or quaternizing agent. If the monomers to be polymerized are not soluble, they can be reacted in a non-solvent by means of precipita-tion polymerization; the material obtained by precipitation - polymerization can then be dissolved in aqueous phase, which can contain the neutralizing or quaternizing agent.
Neutralizing or quaternizing agents in aqueous solution can be added throughout the polymerization, but it is also pos-sible to defer their addition until the end of the pol~mer-ization.
If there is a high content of non-water-soluble co-monomers, emulsion polymerization can also be carried out, an aqueous composition according to the invention subse-quently being produced by neutralization or quaternization.
During emulsion polymerization it may be useful to add sub-stances which lead to a reduction in the viscosity. Mo-lecular weight regulators can also be added to prevent the molecular weight from becoming undesirably high, e.g., greater than 1,000,000.
The practice of the invention may be further illus-trated, by means of non-limiting preferred examples de-scribed below.
Example 1:
An aqueous coating composition, including a copolymer having a glass transition temperature of about 15 C, was prepared as described below.
Initially, four solutions were prepared with composi-tions as follows:
Starting Solution 41.8 parts by weight of water 2~C~3~8~

0.1 parts by weight of 2,2'-azo-bis-(2-amidinopropane) dihydro~hloride (a polymerization catalys~) Input Solution 1 16.9 parts by weight of dimethylamino ethyl methacrylate 16.9 parts by weight of methyl methacrylate Input Solution 2 0.2 parts by weight of polymerization catalyst (as above) 2.0 parts by weight of water Neutralization Solution 15.8 parts by weight of water about 6.3 parts by weight of 85 ~ phosphoric acid These solutions provide a total of about 100 parts by weight, of which about 40% is copolymer solicls after re-action, with the balance essentially water.
The synthesis of the copolymer was effected in a re-action vessel equipped with an agitator, heating means, cooling means, reflux condenser, temperature measurement means, and two feed reservoirs. The starting solution was initially prepared in the reaction vessel from water and catalyst. The input solutions 1 and 2 were put into the separate ~eed reservoirs. The starting solution was heated to 75 C with stirring. Then both input solutions were slowly and simultaneously added to the reaction vessel con-taining the starting solution over a period of 90 minutes, during which time the temperature climbed to 85 C. After the addition was complete, the reaction mixture was stirred at 80 C for 60 minutes. Then, after being cooled to a temperature below 45 C, the dispersion was adjusted with - the neutralizing solution to a pH value of about 5.5.
The reaction product thus obtained was a clear so-lution with a viscosity of more than 5 pascal seconds ("Pa s"), as measured by a ~rookfield viscosimeter using spindle 4 at 20 revolutions per minute ("rpm"); the dry residue amounted to 40 ~ by weight, as determined by evap-oration under oil pump vacuum at 80 C.
The following results were obtained when the adhesive 20~33~

properties of the solution were tested:
Method (coating) The following investigation was carried out with a composition prepared by mixing a portion of the copvlymer solution prepared as described in Example 1 with an equal amount of water, to produce an aqueous composition contain-ing 20 % by weight of copolymer solids.
The turbid, yellowish liquid had a pH value of 5.4 +
1. The specific gravity at 20 C was 1.056 + 0.1. The viscosity measured with a Ford cup using a 4 millimeter ("mm") orifice was 24 + 2 seconds ("sec"). The chemical oxygen demand ("COD") value, measured by the Dr. ~ange cu-vetke test, was 357 grams ("g") of 2 per liter (~1~). The Abel-Pensky flash point was determined to be more than 100 C. For the test coating a) a glass plate and b) a painted steel sheet were covered with a 10 to 20 micron thick coat-ing, using a spray gun.
The coating was left to dry at room temperature on both base surfaces for 15 to 20 minutes. A transparent, hard film resulted.
The applied coating was then dissolved with water at room temperature, using a hand hald shower head, operated at a pressure of 2 to 3 bars. After less than 1 minute the whole film was dissolved.
The COD value of the rinsing water, measured as above, for a mixture of 20 g of the copolymer composition accord-- ing to the invention and 10 1 of tap water was 433 mg 02/l.
Additional examples of compositions according to the invention were prepared in the same manner as Example 1, except for the changes in reacted monomers, degree of dilu-~ tion with water, and neutralizing acid used as specified `. under specific example numbers below.
Example 2:
" The monomeric components were ethyl acrylate (''EAI'), 70% by weight, and dimethylamino ethyl methacrylate ('ID~EM''), 30% by weight. An aqueous composition with 35%
solids, neutralized with sulfuric acid, was prepared.

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Example 3:
The monomeric components were 70~ by weight of dimeth-ylamino propyl methacrylamide ("D~PMA") and 30~ by weight of EA. An aqueous composition with 30% by weight solids, neutralized with glacial acetic acid, was prepared.
Example 4:
The monomeric components were 85% by weight of DMAPMA
and 15% by weight of butyl acrylate ("BuA"). An aqueous composition with 30~ by weight solids, neutralized with formic acid : phosphoric acid in a ratio of 2 : 5 parts by weight, was prepared.
Example 5:
The monomeric components were 80% by weight of DMAEM
and 20~ by weight of methyl methacrylate ("MMA"). ~n aque-ous composition with 35~ by weight solids, neutralized with formic acid, was prepared.
Exam~le 6:
The monomeric components were 40 % by weight of DMAEM, 20 ~ by weight of MMA, 20 % by weight of EA, and 20 % by weight of BuA. An aqueous composition with 40% by weight solids, neutralized with phosphoric acid, was prepared.
The compositions in Examples 2 to 6 were tested by surface coating as with the composition from Example 1.
. All the Examples 2 - 6, like Example l, produced clear .~ 25 coatings that could easily be removed with cold water under slight pressureO

Claims

1. A process comprising the steps of:
(I) coating a solid, water resistant surface with a liquid film of a homogeneous composition of mat-ter that comprises water and copolymer molecules selected from the group consisting of:
(A) copolymer molecules preparable by copolymer-ization of:
(a) a component of nitrogen-free olefinic monomer molecules; and (b) a component or linearly-polymerizable monomers each containing at least one tertiary amine functional group, the relative amounts of components (a) and (b) being such that component (a) represents from 15% to 90% by weight of the total of components (a) and (b);
(B) copolymer molecules preparable by totally or partially neutralizing the tertiary amine functional groups of a copolymer molecule of type (A) with acid;
(C) copolymer molecules preparable by totally or partially quaternizing the tertiary amine functional groups of a copolymer of type (A) to convert the tertiary amine functional groups to quaternary ammonium salt groups;
and (D) copolymer molecules preparable by partially neutralizing the tertiary amine functional groups of a copolymer molecule of type (A) with acid and also totally or partially quaternizing the remaining tertiary amine functional groups of the copolymer of type (A) to convert these tertiary amine func-tional groups to quaternary ammonium salt groups;

(II) drying the liquid film coated in step (I) to pro-duce therefrom a solid film adherent to the solid, water resistant surface coated in step (I);
(III) depositing on the solid film produced in step (II) solids of a composition chemically distinct from that of the solid film produced in step (II); and (IV) removing from the solid, water resistant surface coated in step (I) the solid film produced in step (II) together with the solids deposited thereon in step (III) by washing with liquid wat-er.

2. A process according to claim 1, wherein the molecules of component (a) are selected from the group consist-ing of acrylic acid, methacrylic acid, and esters of acrylic acid and methacrylic acid with monoalkanols containing from 1 to 4 carbon atoms, with at least 50 % of the total weight of component (a) being selected from esters rather than free acids.

3. A process according to claim 2, wherein the molecules of component (B) are selected from the group consist-ing of esters of acrylic acid and methacrylic acid with monoalcohols containing a total from 4 to lo car-bon atoms and including one substituent, on a carbon atom not directly attached to oxygen, that is dimeth-ylamino, diethylamino, or methylethylamino.

4. A process according to claim 1, wherein the molecules of component (B) are selected from the group consist-ing of esters of acrylic acid and methacrylic acid with monoalcohols that contain a total from 4 to 10 carbon atoms and that include one substituent, on a carbon atom not directly attached to oxygen, that is dimekhylamino, diethylamino, or methylethylamino.

5. A process according to claim 4, wherein the liquid composition coated in step (I) comprises from 5 % to 75 % by weight, based on the total composition, of copolymer molecules as recited in step (I).

6. A process according to claim 3, wherein the liquid composition coated in step (I) comprises from 5 % to 75 % by weight, based on the total composition, of copolymer molecules as recited in step (I).

7. A process according to claim 2, wherein the liquid composition coated in step (I) comprises from 5 % to 75 % by weight, based on the total composition, of copolymer molecules as recited in step (I).

8. A process according to claim 1, wherein the liquid composition coated in step (I) comprises from 5 % to 75 % by weight, based on the total composition, or copolymer molecules as recited in step (I).

9. A process according to claim 1, wherein the copolymer employed in step (I) has a glass transition tempera-ture in the range of from -30° C to +50° C.

10. A process according to claim 1, wherein the solid, water resistant surface coated in step (I) includes a wall surface of a spray coating booth and the liquid composition coated in step (I) contains from 15 % to 50 % by weight of copolymer component, based on the composition as a whole.

11. A process according to claim 10, wherein the aqueous composition coated in step (I) has a pH value not greater than 7, as a result of the presence of a suf-ficient fraction of acid neutralized tertiary amine functional groups in the copolymer content of the aqueous composition.

12. A process according to claim 11, in which the neutral-ization of some of the tertiary amine functional groups in the copolymer content of the aqueous compos-ition coated in step (I) is accomplished with phos-phoric acid.

13. A process according to claim 10, wherein at least some of the copolymer content of the aqueous composition coated in step (I) is selected from groups (C) and (D).

14 14. A homogeneous aqueous composition of matter comprising a concentration of from 5 to 75 % by weight, based on the composition as a whole, of water soluble copoly-mers selected from the group consisting of:
(A) copolymer molecules preparable by copolymeriza-tion of:
(a) a component of nitrogen-free olefinic mono-mer molecules; and (b) a component of linearly-polymerizable mono-mers each containing at least one tertiary amine functional group, the relative amounts of components (a) and (b) being such that component (a) represents from 15%
to 90% by weight of the total of components (a) and (b);
(B) copolymer molecules prepayable by totally or par-tially neutralizing the tertiary amine functional groups of a copolymer molecule of type (A) with acid;
(C) copolymer molecules preparable by totally or par-tially quaternizing the tertiary amine functional groups of a copolymer of type (A) to convert the tertiary amine functional groups to quaternary ammonium salt groups; and (D) copolymer molecules preparable by partially neu-tralizing the tertiary amine functional groups of a copolymer molecule of type (A) with acid and also totally or partially quaternizing the re-maining tertiary amine functional groups of the copolymer of type (A) to convert these tertiary amine functional groups to quaternary ammonium salt groups, with not all of the copolymer molecules being of type (A).

15. A composition according to claim 14 wherein the mole-cules of component (a) are selected from the group consisting of acrylic acid, methacrylic acid, and esters of acrylic acid and methacrylic acid with mono-alkanols containing from 1 to 4 carbon atoms, with at least 50 % of the total weight of component (a) being selected from esters rather than free acids.

16. A composition according to claim 15, wherein the mole-cules of component (b) are selected from the group consisting of esters of acrylic acid and methacrylic acid with monoalcohols containing a total from 4 to 10 carbon atoms and including one substituent, on a car-bon atom not directly attached to oxygen, that is di-methylamino, diethylamino, or methylethylamino.

17. A composition according to claim 14, wherein the mole-cules of component (B) are selected from the group consisting of esters of acrylic acid and methacrylic acid with monoalcohols that contain a total from 4 to 10 carbon atoms and that include one substituent, on a carbon atom not directly attached to oxygen, that is dimethylamino, diethylamino, or methylethylamino.

18. A composition according to claim 14, comprising from 5 % to 75 % by weight, based on the total composition, of copolymer molecules.

19. A composition according to claim 14, wherein the co-polymer has a glass transition temperature in the range of from -30° C to +50° C.

20. A composition according to claim 16, wherein said copolymer is present in a concentration in the range of from 15 % to 50 % by weight, based on the composi-tion as a whole, and monomer type (a) constitutes from 15 % to less than 70 % by weight of the total of mono-mer types (a) and (b).