WO1995004608A1 - Composition and process for prepainting treatment of plastics - Google Patents

Composition and process for prepainting treatment of plastics Download PDF

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Publication number
WO1995004608A1
WO1995004608A1 PCT/US1994/008696 US9408696W WO9504608A1 WO 1995004608 A1 WO1995004608 A1 WO 1995004608A1 US 9408696 W US9408696 W US 9408696W WO 9504608 A1 WO9504608 A1 WO 9504608A1
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WO
WIPO (PCT)
Prior art keywords
component
acids
group
treatment
aqueous solution
Prior art date
Application number
PCT/US1994/008696
Other languages
French (fr)
Inventor
Osamu Furuyama
Kuzunari Hamamura
Masahiro Motozawa
Original Assignee
Henkel Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Henkel Corporation filed Critical Henkel Corporation
Priority to US08/596,249 priority Critical patent/US5750198A/en
Publication of WO1995004608A1 publication Critical patent/WO1995004608A1/en

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Classifications

    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/12Chemical modification
    • C08J7/14Chemical modification with acids, their salts or anhydrides
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B05SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05DPROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/10Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by other chemical means
    • B05D3/101Pretreatment of polymeric substrate
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/04Coating
    • C08J7/043Improving the adhesiveness of the coatings per se, e.g. forming primers
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/04Coating
    • C08J7/06Coating with compositions not containing macromolecular substances
    • C08J7/065Low-molecular-weight organic substances, e.g. absorption of additives in the surface of the article

Definitions

  • the invention relates to a water-based liquid composition for treating plas ⁇ tics, particularly plastic moldings, more particularly those made of polypropylene, polyurethane, and the like, that are used, e.g., as body panels, bumpers, or the
  • the invention is especially suited to prepainting treatment of such plastics.
  • the invention is accordingly described below primarily with ref ⁇ erence to prepainting treatment for plastic moldings, but more generalized appli ⁇ cation to plastic surfaces is within the scope of the invention.
  • Background Art 0 The plastic moldings used for automotive bumpers, etc., usually are cur ⁇ rently manufactured by injection molding. In the case of resins that are prone to stick to the mold, such as polyurethane, the mold surface is usually coated prior to actual molding with a wax-based external release agent, and a metal soap (for example, zinc stearate), which functions as an internal release agent, is also fre-
  • the treatment of plastic moldings prior to painting has heretofore consist ⁇ ed mainly of the use of solvent cleaners such as 1 ,1 ,1-trichloroethane, freons, and the like.
  • solvent cleaners such as 1 ,1 ,1-trichloroethane, freons, and the like.
  • This type of treatment can dissolve and remove release agents and also has an excellent operating efficiency due to its ease of drying.
  • environmental considerations have made the development of sub ⁇ stitute pretreatment methods a matter of urgency.
  • the present invention is directed to an inhibition of the surface bleed by internal plastic additives that occurs with elapsed time and during the drying step in the interval after the water-based treatment of plastic moldings preparatory to their painting. More specifically, the present invention takes as its objects an in ⁇ crease in the drying temperature in order thereby to support equipment downsiz- ing, an improvement in the paintability (e.g., paint crawling, paint adherence), and/or in particular a stabilization of the paintability through an inhibition of time- wise changes in the paint-receiving surface.
  • an improvement in the paintability e.g., paint crawling, paint adherence
  • stabilization of the paintability through an inhibition of time- wise changes in the paint-receiving surface.
  • one embodiment of the present invention is a water-based liquid composition for treating plastic moldings prior to the painting thereof, wherein said composition is an aqueous solution that, in addition to water, comprises, preferably consists essentially of, or still more preferably consists of at least 0.05 weight % of at least one selection from carboxylic acids that do not contain any terminal alkyl group in their molecular structure and hydroxycarboxylic acids that do not contain any terminal alkyl group in their molecular structure; optionally, the compositions according to the invention may also contain surfactants, other builders, and/or other acids.
  • a process according to the invention includes at a minimum a step of contacting a plastic surface with a composition according to the invention as described herein.
  • the prepaint treatment agent is an aqueous solution that contains as its essential component at least one selection from carboxylic acids that do not contain any terminal alkyl group in their molecular structure and hydroxycarboxylic acids that do not contain any terminal alkyl group in their molecular structure.
  • the absence of any terminal alkyl group from the molecular structure means that no group having the formula -C n H 2n+1 is present in the molecule.
  • Terminal alkyl-free carboxylic acids are specifically exemplified by oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid.
  • Terminal alkyl-free hydroxycarboxylic acids are specifically exemplified by giycolic acid, malic acid, tartaric acid, and citric acid.
  • the aqueous solution preferably contains at least 0.05 weight % and more preferably at least 0.1 weight % of the one or more selections from terminal alkyl- free carboxylic acids and terminal alkyl-free hydroxycarboxylic acids.
  • the sur ⁇ face bleed of internal additives from within the plastic molding usually is not ade ⁇ quately inhibited at below 0.05 weight %.
  • the aqueous solution according to the invention preferably contains not more than 5, or more preferably not more than 2.2 weight % of these acids.
  • aqueous solution in accordance with the present invention functions to inhibit bleed-out by internal additives present in the plastic molding.
  • a surfactant normally must also be used to remove other contamin ⁇ ants, for example dust and oil, that adhere after molding.
  • Said surfactant may be used in the prepaint treatment agent of the invention in combination with or ⁇ ganic acid as specified above for the invention.
  • contaminants such as dust and oil may first be removed using a solution that contains surfactant and treatment may then be carried out using a surfactant-free prepaint treatment agent in accordance with the invention.
  • the prepaint treatment agent of the invention may contain other builders.
  • Plastic moldings can be treated with the prepaint treatment agent of the invention by spraying or immersion.
  • the bath temperature is not critical to the effect of the invention, i.e., the inhibition of bleed-out by internal additives. How ⁇ ever, when surfactant is present in the prepaint treatment agent of the invention and this agent is relied on for general cleaning as well as for the inhibition of bleed-out, the temperature should be selected as a function of such considera ⁇ tions, generally known in the art, as the adhesion status of any oil, dust, or the like in order to accomplish their removal by the surfactant.
  • Treatment with the water-based pretreatment agent of the invention is believed to increase the surface free energy of plastic surfaces. This effect is not destroyed even by water washing after treatment and is not degraded by drying or by the passage of time after drying. It is thought that the inhibition of surface bleed by internal additives is caused by this increase in the surface free energy of the plastic surface.
  • the organic acids specified for the present invention do not contain any terminal alkyl group in the molecule. In fact, however, terminal alkyl-containing organic acids do appear to produce an increase in the surface free energy immediately after treatment, but with these compounds the surface free energy is reduced by drying and by the elapse of time. It is for this reason that the use of alkyl-containing organic acids does not yield an adequate im- provement in the paintability.
  • the modification of surface properties as a result of execution of the prepaint treatment of the invention results in an improved wettability by aqueous solutions and thus in improved drying characteristics.
  • Pretreatment aoent 1 (corresponds to a prepaint treatment agent of the invention) sulfuric acid: 3 wt % polyoxyethylene nonylphenyl ether 0.5 wt % organic acid i see Table 1 water remainder Pretreatment agent 2
  • sulfuric acid 3 wt % polyoxyethylene nonylphenyl ether 0.5 wt %
  • Method A treatment with pretreatment agent 1 (180 sec, 80° C) i water wash (30 sec, ambient temperature)
  • Method B treatment with pretreatment agent 2 (180 sec, 80° C)
  • Method C treatment with pretreatment agent 4 (180 sec, 80° C) i drain and dry (10 min, 80° C or 120° C)
  • Holding conditions 1 painted within 12 hours after pretreatment. Holding conditions 2: painted on the fifth day after pretreatment. Primers:
  • Comparative Examples 5 to 7 which used terminal alkyl-containing organ ⁇ ic acids, gave approximately the same initial contact angle values as Examples 1 to 6, but had inferior values for the timewise variation in the contact angle, ad- hesion after water soak, and paint crawling. This was true despite use of the ter ⁇ minal alkyl-containing organic acids at concentrations of 0.5 to 2.0 weight %. Benefits of the Invention
  • the surface bleed of internal additives present in plastic moldings is inhib ⁇ ited by treatment with the water-based prepaint treatment agent in accordance with the present invention. This results in the following highly desirable effects: high-temperature drying becomes possible, which supports a shortening of the drying time and equipment downsizing; and changes in the surface with elapsed time are inhibited; this stabilizes the paintability and improves the workability.

Abstract

Water-based liquid compositions for treating plastic moldings prior to the painting thereof contain as essential component at least 0.05 weight % of at least one selection from carboxylic acids that do not contain any terminal alkyl group in their molecular structure and hydroxycarboxylic acids that do not contain any terminal alkyl group in their molecular structure. The surface bleed of the internal additives present in plastic moldings can be inhibited by treatment with the water-based prepaint treatment compositions in accordance with the present invention. This results in an inhibition of timewise changes in the paint-receiving surface and thus stabilizes the paintability.

Description

Description COMPOSITION AND PROCESS FOR PREPAINTING TREATMENT OF PLASTICS
Technical Field
The invention relates to a water-based liquid composition for treating plas¬ tics, particularly plastic moldings, more particularly those made of polypropylene, polyurethane, and the like, that are used, e.g., as body panels, bumpers, or the
5 like in automobiles. The invention is especially suited to prepainting treatment of such plastics. The invention is accordingly described below primarily with ref¬ erence to prepainting treatment for plastic moldings, but more generalized appli¬ cation to plastic surfaces is within the scope of the invention. Background Art 0 The plastic moldings used for automotive bumpers, etc., usually are cur¬ rently manufactured by injection molding. In the case of resins that are prone to stick to the mold, such as polyurethane, the mold surface is usually coated prior to actual molding with a wax-based external release agent, and a metal soap (for example, zinc stearate), which functions as an internal release agent, is also fre-
15 quently added to such resins in advance of molding. Various additives other than internal release agent often are also blended into resins for the purpose of im¬ proving the strength, improving paint adherence, improving the resistance to ag¬ ing, and the like. As a result, during the molding process the strongly hydrophob- ic internal additives and of course any internal release agent bleed onto the sur-
20 face to some degree. The presence on the surface of substances such as ex¬ ternal release agent and bled-out internal additives impairs the post-painting ad¬ herence by the paint film and also causes paint crawling and thereby compromis¬ es the appearance of the paint film. The preparatory treatment that precedes painting must therefore not only remove contaminants adhering after molding,
25 such as dust and oil, but must also remove substances such as external release agent and internal additives that have bled onto the surface.
The treatment of plastic moldings prior to painting has heretofore consist¬ ed mainly of the use of solvent cleaners such as 1 ,1 ,1-trichloroethane, freons, and the like. This type of treatment can dissolve and remove release agents and also has an excellent operating efficiency due to its ease of drying. However, as is well known, environmental considerations have made the development of sub¬ stitute pretreatment methods a matter of urgency.
Cleaning with acidic and alkaline water-based cleaners and cleaning with emulsified solvent cleaners have been investigated as substitute pretreatment methods. These methods differ from solvent cleaning in that they require a rinse step and therefore require a drying step (see Japanese Laid Open Patent Appli¬ cation Numbers Hei 4-27472 [27,472/1992] and Hei 5-39499 [39,499/1993]). However, even after release agent on the surface has been removed by cleaning, drying must be conducted at low temperatures since internal release agent and strongly hydrophobic internal additives bleed onto the surface during the drying step. This lengthens the drying time and thus necessitates the use of large-scale equipment. In addition, since internal release agents and strongly hy¬ drophobic internal additives gradually bleed onto the surface even at room tern- perature, the paintability also becomes impaired when a lengthy period of time is allowed to elapse between cleaning and painting. This requires that the cleaned molding be promptly painted.
As described above, research has heretofore focused on the removal of internal additives once they have bled onto the surface of the plastic molding from within the molding; however, up to now in the knowledge of the applicants there have been no investigations into the inhibition of bleed-out by internal addi¬ tives onto the surface. Disclosure of the Invention
Problems to Be Solved bv the Invention The present invention is directed to an inhibition of the surface bleed by internal plastic additives that occurs with elapsed time and during the drying step in the interval after the water-based treatment of plastic moldings preparatory to their painting. More specifically, the present invention takes as its objects an in¬ crease in the drying temperature in order thereby to support equipment downsiz- ing, an improvement in the paintability (e.g., paint crawling, paint adherence), and/or in particular a stabilization of the paintability through an inhibition of time- wise changes in the paint-receiving surface. Summary of the Invention The inventors discovered that treating the surface of a plastic molding with an aqueous solution containing specific organic acids results in an inhibition of the surface bleed by internal plastic additives and thus in an inhibition of timewise changes in the paint-receiving surface and a stabilization of the paintability. In specific terms, one embodiment of the present invention is a water-based liquid composition for treating plastic moldings prior to the painting thereof, wherein said composition is an aqueous solution that, in addition to water, comprises, preferably consists essentially of, or still more preferably consists of at least 0.05 weight % of at least one selection from carboxylic acids that do not contain any terminal alkyl group in their molecular structure and hydroxycarboxylic acids that do not contain any terminal alkyl group in their molecular structure; optionally, the compositions according to the invention may also contain surfactants, other builders, and/or other acids. A process according to the invention includes at a minimum a step of contacting a plastic surface with a composition according to the invention as described herein.
Description of Preferred Embodiments The most important characteristic of the water-based composition or agent in accordance with the present invention for treating plastic moldings prior to their painting (hereinafter abbreviated as the prepaint treatment agent) is that said agent is an aqueous solution that contains as its essential component at least one selection from carboxylic acids that do not contain any terminal alkyl group in their molecular structure and hydroxycarboxylic acids that do not contain any terminal alkyl group in their molecular structure. For the purposes of the present invention, the absence of any terminal alkyl group from the molecular structure means that no group having the formula -CnH2n+1 is present in the molecule.
Terminal alkyl-free carboxylic acids are specifically exemplified by oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid. Terminal alkyl-free hydroxycarboxylic acids are specifically exemplified by giycolic acid, malic acid, tartaric acid, and citric acid.
The aqueous solution preferably contains at least 0.05 weight % and more preferably at least 0.1 weight % of the one or more selections from terminal alkyl- free carboxylic acids and terminal alkyl-free hydroxycarboxylic acids. The sur¬ face bleed of internal additives from within the plastic molding usually is not ade¬ quately inhibited at below 0.05 weight %. Independently, for reasons of econ- omy, the aqueous solution according to the invention preferably contains not more than 5, or more preferably not more than 2.2 weight % of these acids.
The aqueous solution in accordance with the present invention as de¬ scribed above (= aqueous solution that contains at least one selection from ter¬ minal alkyl-free carboxylic acids and terminal alkyl-free hydroxycarboxylic acids) functions to inhibit bleed-out by internal additives present in the plastic molding. However, a surfactant normally must also be used to remove other contamin¬ ants, for example dust and oil, that adhere after molding. Said surfactant may be used in the prepaint treatment agent of the invention in combination with or¬ ganic acid as specified above for the invention. Alternatively, contaminants such as dust and oil may first be removed using a solution that contains surfactant and treatment may then be carried out using a surfactant-free prepaint treatment agent in accordance with the invention.
No particular restrictions apply to the surfactant, and its type and quantity of use should be selected as a function of the particular conditions, such as the nature of the resin, the status of adhesion of the dust and oil, etc.
In addition to surfactant, the prepaint treatment agent of the invention may contain other builders.
Plastic moldings can be treated with the prepaint treatment agent of the invention by spraying or immersion. The bath temperature is not critical to the effect of the invention, i.e., the inhibition of bleed-out by internal additives. How¬ ever, when surfactant is present in the prepaint treatment agent of the invention and this agent is relied on for general cleaning as well as for the inhibition of bleed-out, the temperature should be selected as a function of such considera¬ tions, generally known in the art, as the adhesion status of any oil, dust, or the like in order to accomplish their removal by the surfactant.
Treatment with the water-based pretreatment agent of the invention is believed to increase the surface free energy of plastic surfaces. This effect is not destroyed even by water washing after treatment and is not degraded by drying or by the passage of time after drying. It is thought that the inhibition of surface bleed by internal additives is caused by this increase in the surface free energy of the plastic surface. The organic acids specified for the present invention do not contain any terminal alkyl group in the molecule. In fact, however, terminal alkyl-containing organic acids do appear to produce an increase in the surface free energy immediately after treatment, but with these compounds the surface free energy is reduced by drying and by the elapse of time. It is for this reason that the use of alkyl-containing organic acids does not yield an adequate im- provement in the paintability.
*
Moreover, the modification of surface properties as a result of execution of the prepaint treatment of the invention results in an improved wettability by aqueous solutions and thus in improved drying characteristics.
The invention and its benefits may be further appreciated by consideration of the following Examples (according to the invention) and Comparative Examp¬ les (not according to the invention).
Examples and Comparative Examples
JL Test materials amine-cured polyurethane (bumper material) external release agent: oxidized wax type internal release agent: zinc stearate hard polypropylene (bumper material) Composition of the pretreatment agents Pretreatment aoent 1 (corresponds to a prepaint treatment agent of the invention) sulfuric acid: 3 wt % polyoxyethylene nonylphenyl ether 0.5 wt % organic acid i see Table 1 water remainder Pretreatment agent 2
(not a prepaint treatment agent of the invention) sulfuric acid 3 wt % polyoxyethylene nonylphenyl ether 0.5 wt %
(HLB: 12) water remainder Pretreatment agent 3
(corresponds to a prepaint treatment agent of the invention) organic acid see Table 1 water remainder Pretreatment agent 4
(corresponds to a prepaint treatment agent of the invention) polyoxyethylene nonylphenyl ether 0.5 wt %
(HLB: 12) organic acid see Table 1 water remainder
3-. Treatment methods
Method A: treatment with pretreatment agent 1 (180 sec, 80° C) i water wash (30 sec, ambient temperature)
wash with pure water (30 sec, ambient temperature)
drain and dry (10 min, 80° C or 120° C)
Method B: treatment with pretreatment agent 2 (180 sec, 80° C)
water wash (30 sec, ambient temperature)
treatment with pretreatment agent 3 (10 sec, ambient temperature) wash with pure water (30 sec, ambient temperature) i drain and dry (10 min, 80° C or 120° C)
Method C: treatment with pretreatment agent 4 (180 sec, 80° C) i drain and dry (10 min, 80° C or 120° C)
(Spraying was used for treatment with the pretreatment agent and for the water washes.) 4 Painting
After pretreatment, the sample was held as specified below and then painted.
Holding conditions 1 : painted within 12 hours after pretreatment. Holding conditions 2: painted on the fifth day after pretreatment. Primers:
In the case of the amine-cured polyurethane: Soflex® 1000 from Kansai Paint Kabushiki Kaisha, baking for 15 minutes at 110° C, film thickness = 15 to 20 mi¬ crometers;
In the case of the hard polypropylene: Soflex® 2500 from Kansai Paint Kabushi- ki Kaisha, baking for 10 minutes at 100° C, film thickness = 15 to 20 micrometers Top coat:
The following was used as the top coat for both sample materials: Sof¬ lex® 1200 from Kansai Paint Kabushiki Kaisha, baking for 20 minutes at 120° C, film thickness = 35 to 40 micrometers. 5,. Test methods used for evaluation (Contact angle)
After the execution of the pretreatment and drain and dry, or for other samples after completion of the holding period in addition, a drop of distilled wat¬ er was placed on the surface of the sample and the contact angle was measured with a goniometer-type contact angle instrument. (The value measured immedi¬ ately after drain and dry only is designated "initial" below.) Lower contact angles are indicative of lower interfacial energies between water and the treated solid surface and hence of better paintabilities. (Adhesion after Water Soak)
After a holding period of 24 hours after painting, a checkerboard pattern of 100 squares, each 2 mm on a side, was cut in the paint surface using a sharp cutter. After an ensuing immersion for 240 hours in de-ionized water at 40° C, cellophane tape was applied to the checkerboard and then shaφiy peeled off and the number of residual paint film squares was counted. A larger number of re¬ sidual squares is indicative of a better adhesion. (Paint crawling test)
The appearance of the primer was visually evaluated after its application and was scored on the following three-level scale,
+ + no primer crawling was observed
+ orange-peel crawling was observed X crawling is observed to such a degree that the substrate has become visible The results of the performance evaluations are reported in Table 1 , and these results support the following conclusions:
1. The contact angle, whether measured initially or after the holding period, was smaller and its variation was less in Examples 1 to 6 of the invention than in
Comparative Examples 1 to 7. This was true even when high temperature paint- baking conditions were employed. The adhesion after water soak was excellent in Examples 1 to 6, and no paint crawling was observed in Examples 1 to 6. These excellent property values confirmed the inhibition of internal additive bleed from the plastic moldings.
2. In Examples 1 to 6 of the invention, the differences among treatment meth¬ ods A, B, and C did not cause differences among the initial contact angle values, the timewise variation in the contact angle values, the adhesion after water soak, or paint crawling. This indicates that there is no difference between use of the surfactant in the prepaint treatment agent of the invention and preliminary treat¬ ment with a solution that contains only surfactant followed by treatment with sur¬ factant-free prepaint treatment agent in accordance with the present invention. Table 1 : TEST VARIABLES AND RESULTS OF THE PERFORMANCE
EVALUATIONS
Pre¬ Organic Acid Initial Contact Drain/ Hold¬ treat¬ Angle in Degrees Dry ing ment On: Temp., Condi¬ Code ° C tion
Type % PU PP Code Cone.
Ex. 1 A Succinic 0.5 66 97 120 1
Ex. 2 B Malic 0.1 67 99 80 2
Ex.3 C Tartaric + 0.3 64 83 120 1 Citric
Ex. 4 C Malonic 1.0 65 85 80 2
Ex. 5 A Oxalic 0.05 68 100 120 1
Ex. 6 B Citric 2.0 65 99 120 1
C Ex. A none - 82 98 120 1
1
C Ex. A none - 83 101 80 2
2
C Ex. B Malic 0.03 80 99 120 1
3
C Ex. B Tartaric 0.01 79 98 80 2
4
C Ex. A Methyl 1.0 67 100 120 1
5 Succinic
C Ex. B Lactic 2.0 68 98 120 1 6
C Ex. C Acetic 0.5 65 102 80 2
7
Notes for Table 1 "PU" = Polyurethane; "PP" = Polypropylene; "Ex." = [Working] Example; "C. Ex."
= Comparative Example (Table 1 is continued on the next page) Table 1 continued
For Polyurethane: For Polypropylene
Contact Adhe¬ Paint Contact Adhe¬ Paint Angle, ° sion Crawl¬ Angle, ° sion Crawl¬ After ing After ing Water Water Soak Soak
Ex. 1 66 100 ++ 98 100 ++
Ex. 2 68 100 -H- 100 100 ++
Ex. 3 64 100 ++ 82 100 -H-
Ex. 4 64 100 -H- 86 100 ++
Ex. 5 69 100 ++ 101 100 ++
Ex. 6 65 100 -H- 96 100 ++
C. Ex. 1 106 29 X 112 94 +
C Ex. 2 92 82 + 108 96 +
C Ex. 3 98 67 X 110 95 +
C Ex. 4 86 94 + 110 97 +
C Ex. 5 102 32 X 109 94 +
C Ex. 6 98 56 X 110 93 +
C Ex. 7 85 96 + 109 97 +
Notes for Table 1 continued
Values for contact angle in columns in which the words "Contact Angle" in the column heading are not immediately preceded by the word "Initial" were measured on the treated surfaces after pretreatment, followed by drain and dry and then followed by the holding period, but before painting the surface.
3. The values for the property set (initial contact angle value, timewise vari¬ ation in the contact angle value, adhesion after water soak, and paint crawling) in Comparative Examples 1 and 2 (with no addition of organic acid) were inferior to those of Examples 1 to 6. 4. Comparative Examples 3 and 4 did employ terminal alkyl-free organic acids, but at concentrations of 0.01 to 0.03 weight %, or lower than the 0.05 to 2.0 weight % used in Examples 1 to 6. The values for the property set (initial contact angle value, timewise variation in the contact angle value, adhesion after water soak, and paint crawling) were again inferior. This indicates that 0.05 weight % is a critical organic acid concentration value with regard to the develop¬ ment of the effects of the invention.
5. Comparative Examples 5 to 7, which used terminal alkyl-containing organ¬ ic acids, gave approximately the same initial contact angle values as Examples 1 to 6, but had inferior values for the timewise variation in the contact angle, ad- hesion after water soak, and paint crawling. This was true despite use of the ter¬ minal alkyl-containing organic acids at concentrations of 0.5 to 2.0 weight %. Benefits of the Invention
The surface bleed of internal additives present in plastic moldings is inhib¬ ited by treatment with the water-based prepaint treatment agent in accordance with the present invention. This results in the following highly desirable effects: high-temperature drying becomes possible, which supports a shortening of the drying time and equipment downsizing; and changes in the surface with elapsed time are inhibited; this stabilizes the paintability and improves the workability.

Claims

Claims
1. A process for treating the surface of plastic materials by contacting said surface, for a sufficient time at a sufficient temperature to decrease the spreading angle of water on said surface from the value of the spreading angle of water on said surface before treating, with an aqueous solution consisting essentially of water and:
(A) a total of at least 0.05 weight % of one or more acids selected from the group consisting of carboxylic acids that do not contain any terminal alkyl group in their molecular structure and hydroxycarboxylic acids that do not contain any terminal alkyl group in their molecular structure; and, op¬ tionally, one or more of:
(B) a component selected from acids that are not part of component (A) and
(C) a component of surfactants not part of component (A) or (B).
2. A process according to claim 1 , wherein the plastic surface is that of an article produced by injection molding.
3. A process according to claim 2, wherein the amount of component (A) in the aqueous solution used for treatment is at least 0.1 weight %.
4. A process according to claim 1 , wherein the amount of component (A) in the aqueous solution used for treatment is at least 0.1 weight %.
5. A process according to claim 4, wherein component (A) is selected from the group consisting of oxalic, malonic, succinic, glutaric, adipic, glyclolic, malic, tartaric, and citric acids.
6. A process according to claim 3, wherein component (A) is selected from the group consisting of oxalic, malonic, succinic, glutaric, adipic, glyclolic, malic, tartaric, and citric acids.
7. A process according to claim 2, wherein component (A) is selected from the group consisting of oxalic, malonic, succinic, glutaric, adipic, glyclolic, malic, tartaric, and citric acids.
8. A process according to claim 1 , wherein component (A) is selected from the group consisting of oxalic, malonic, succinic, glutaric, adipic, glyclolic, malic, tartaric, and citric acids.
9. The use for the prepainting treatment of plastic surfaces of an aqueous s liquid solution consisting essentially of water and:
(A) a total of at least 0.05 weight % of one or more acids selected from the group consisting of carboxylic acids that do not contain any terminal alkyl group in their molecular structure and hydroxycarboxylic acids that do not contain any terminal alkyl group in their molecular structure; and, optional- o ly, one or more of:
(B) a component selected from acids that are not part of component (A) and
(C) a component of surfactants not part of component (A) or (B).
10. A use according to claim 9, wherein the plastic surface is that of an article produced by injection molding. s
11. A use according to claim 10, wherein the amount of component (A) in the aqueous solution used for treatment is at least 0.1 weight %.
12. A use according to claim 9, wherein the amount of component (A) in the aqueous solution used for treatment is at least 0.1 weight %.
13. A use according to claim 12, wherein component (A) is selected from the 0 group consisting of oxalic, malonic, succinic, glutaric, adipic, glyclolic, malic, tar¬ taric, and citric acids.
14. A use according to claim 11 , wherein component (A) is selected from the group consisting of oxalic, malonic, succinic, glutaric, adipic, glyclolic, malic, tar¬ taric, and citric acids. 5
15. A use according to claim 10, wherein component (A) is selected from the group consisting of oxalic, malonic, succinic, glutaric, adipic, glyclolic, malic, tar¬ taric, and citric acids.
16. A use according to claim 9, wherein component (A) is selected from the group consisting of oxalic, malonic, succinic, glutaric, adipic, glyclolic, malic, tar- 0 taric, and citric acids.
17. An aqueous solution, suitable for use as a prepainting treatment for molded plastic surfaces, that consists essentially of water and:
(A) a total of at least 0.05 weight % of one or more acids selected from the group consisting of carboxylic acids that do not contain any terminal alkyl group in their molecular structure and hydroxycarboxylic acids that do not contain any terminal alkyl group in their molecular structure and
(B) a component of surfactants not part of component (A), and, optionally,
(C) a component selected from acids that are not part of component (A) or (B).
18. An aqueous solution according to claim 17, wherein the amount of com¬ ponent (A) in the aqueous solution is at least 0.1 weight %.
19. An aqueous solution according to claim 18, wherein component (A) is se¬ lected from the group consisting of oxalic, malonic, succinic, glutaric, adipic, gly¬ clolic, malic, tartaric, and citric acids.
20. An aqueous solution according to claim 17, wherein component (A) is se¬ lected from the group consisting of oxalic, malonic, succinic, glutaric, adipic, gly¬ clolic, malic, tartaric, and citric acids.
PCT/US1994/008696 1993-08-11 1994-08-09 Composition and process for prepainting treatment of plastics WO1995004608A1 (en)

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JP5/219176 1993-08-11
JP5219176A JPH0753743A (en) 1993-08-11 1993-08-11 Surface preparation agent for resin molding

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EP0811430A1 (en) * 1996-06-07 1997-12-10 Ppg Industries, Inc. Water repelllent surface treatment with acid activation
FR2774680A1 (en) * 1998-02-10 1999-08-13 Essilor Int PROCESS FOR COATING AN ORGANIC GLASS SUBSTRATE AND TREATMENT SOLUTION
US6025025A (en) * 1990-04-03 2000-02-15 Ppg Industries Ohio, Inc. Water-repellent surface treatment
EP1760129A1 (en) * 2005-09-02 2007-03-07 Sika Technology AG Aqueous primer composition for improving the adherence of adhesives and sealants on painted surfaces
GB2444241A (en) * 2006-11-28 2008-06-04 Poliforce Ltd Polystyrene element with improved mechanical resistance, method for producing it and use thereof
WO2012087227A1 (en) * 2010-12-21 2012-06-28 MAGU E-Systems AB Method for pretreatment of plastic objects before coating

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US3404996A (en) * 1965-05-27 1968-10-08 American Cyanamid Co Method of treating polymeric substrates so as to improve adhesion of mar-resistant surfaces thereto
US3481763A (en) * 1966-07-13 1969-12-02 Owens Illinois Inc Method for controlling the penetration of a siloxane resin into fibrous substrate
US5248525A (en) * 1991-01-24 1993-09-28 Henkel Corporation Treating an autodeposited coating with an alkaline solution containing anions of multifunctional organic acids
US5167992A (en) * 1991-03-11 1992-12-01 Microelectronics And Computer Technology Corporation Selective electroless plating process for metal conductors

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5980990A (en) * 1990-04-03 1999-11-09 Ppg Industries Ohio, Inc. Water repellent surface treatment with acid activation
US6025025A (en) * 1990-04-03 2000-02-15 Ppg Industries Ohio, Inc. Water-repellent surface treatment
EP0811430A1 (en) * 1996-06-07 1997-12-10 Ppg Industries, Inc. Water repelllent surface treatment with acid activation
FR2774680A1 (en) * 1998-02-10 1999-08-13 Essilor Int PROCESS FOR COATING AN ORGANIC GLASS SUBSTRATE AND TREATMENT SOLUTION
WO1999041301A1 (en) * 1998-02-10 1999-08-19 Essilor International Compagnie Generale D'optique Method for coating an organic glass substrate and treating solution
US6416821B1 (en) 1998-02-10 2002-07-09 Essilor International Compagnie General D'optique Method for coating an organic glass substrate and treating solution
EP1760129A1 (en) * 2005-09-02 2007-03-07 Sika Technology AG Aqueous primer composition for improving the adherence of adhesives and sealants on painted surfaces
GB2444241A (en) * 2006-11-28 2008-06-04 Poliforce Ltd Polystyrene element with improved mechanical resistance, method for producing it and use thereof
WO2012087227A1 (en) * 2010-12-21 2012-06-28 MAGU E-Systems AB Method for pretreatment of plastic objects before coating

Also Published As

Publication number Publication date
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CA2168736A1 (en) 1995-02-16

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