CA2035538C - Polyvinyl chloride plastisol composition suitable as a sealant - Google Patents

Abstract

A plastisol based composition contains:
(a) a copolymer of an aliphatic olefinically unsaturated material and an anhydride containing material, and (b) a polyvinyl chloride plastisol.
The composition is particularly suitable for use as a sealant.

Description

POLYVINYL CHLORIDE PLASTISOL COMPOSITION SUITABLE AS A SEALANT
Background of the Invention 4 The present invention relates to polyvinyl chloride pla~tisol compositions, for example sealant compositions.
6 In the manufacture of automobiles, the automobile body is initially primed with a coating composition to prevent corrosion of 8 the metal. This can be done in a number of ways although generally it is performed by cationic electrodeposition using the auto body as the 10 cathode. Once the automobile body has been primed in this manner, subsequent steps in the assembly are carried out. These steps 12 typically include the use of sealants over the primed automobile body. The sealants are subsequently topcoated along with the 14 remainder of the body during the final stages of the painting process.
Polyvinyl chloride plastisols offer several advantages for 16 use as sealant compositions: a good balance of strength, elongation and toughness, ;ni -1 to no volatile organic component and low cost.
18 However, despite these advantageous properties, when used in conjunction with cationically electrodepositable primer compositions 20 in automotive applications, adhesion is poor and yellowing of the topcoat composition results.
22 Historically, polyaminoamides which are art recognized adhesion promoters, have been utilized in an attempt to deal with the 24 above adhesion problems. These, however, can adversely affect the stability of the plastisol based sealant composition, the cure of the 26 topcoat and in addition, cause more yellowing.
There is a need, therefore, for a polyvinyl chloride 28 plastisol based composition which exhibits excellent adhesion to primed metal and is capable of being topcoated with a variety of 30 coating compositions without yellowing of the topcoat.

32 Summary of the Invention In accordance with the present invention, there is provided a 34 plastisol based composition comprising:

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(a) a copolymer of an aliphatic olefinically unsaturated material 2 and an anhydride containing material; and (b) a polyvinyl chloride plastisol.

In a preferred embodiment the invention provides a process for 6 coating a substrate having an electrodeposited coating composition, comprising, 8 (a) applying to 8aid electrodeposited coating composition a plastisol based composition, comprising a polyvinyl chloride plastisol and between about 0.5 and about 20 weight percent based on total weight of the plastisol based composition of a copolymer of a cyclic-aliphatic 12 olefinically unsaturated monomer material or an aliphatic olefinically unsaturated monomer material selected from the group consi~ting of 4 alpha-olefins and dienes and an anhydride cont~n~ng monomer material capable of vinyl addition polymerization; and 16 (b) applying a topcoat over said plastisol based composition.

18 Detailed Descriptio~ of the Tnv~ntion The composition of the present lnvention comprises as one of 20 its principal components a polyvinyl chloride plastisol. A plastisol is a dispersion of powdered polyvinyl chloride resin in a liquid 22 plastlcizer to produce a fluid matrix whlch may range in viscosity from pourable liquid to a heavy paste. The polyvinyl chloride 24 homopolymers or copolymers are typically produced by emulsion polymerization. Once the polymer is produced and dried, it is 26 dispersed in plasticizer The choice of plasticizer depends upon many factors including the desired solids viscosity relationship, 28 processing characteristics and the ultimate desired performance properties. Suitable pla~ticizers include didecyl phthalate, 30diisodecyl phthalate, diisononyl phthalate, trimethyl pentanediol isobutyrate, sucrose benzoate, butyl cyclohexyl phthalate, butyl octyl 32phthalate, isooctyl epoxystearate, dipropylene glycol dibenzoate, di-2-ethylhexyl adipate, diisodecyl adipate, diisodecyl gluterate, 34 dioctyl sebacate and mixtures thereof. Also suitable for use alone or in admixture with the monopolymeric plasticizers are polymeric 36 plasticizers including polymeric benzoates, polymeric adipates, polymeric glutarates, polymeric sebacates, polymeric phthalates and 38 mixtures thereof.

- 2a -It should be understood that polyvinyl chloride homopolymers 2 or copolymers can be prepared either as functional or non-functional polymers. By functional polyvinyl chloride is meant a homopolymer or 4 copolymer (usually with vinyl acetate) of polyvlnyl chloride in which a small amount of comonomer is added which contributes, hydroxyl, 6 carboxyl, anhydride or other side groups to the chain. Examples include carboxyl functional polyvinyl chlorides such as Union 8 Carbide's VMCA and hydroxyl functional polyvinyl chlorides such as Union Carbide's VROH. By non-functional is meant the homopolymer or copolymer without such modification.

20355~8 In one embodiment of the present invention the polyvinyl 2 chloride plastisol is prepared from a mixture of functional and non-functional polyvinyl chloride polymer.
4 Although a brief description of the preparation of vinyl chloride plastisols has been given above, it should be understood that 6 the preparation of these materials is well appreciated by those skilled in the art and further details are not required for practice 8 of the present invention. If further details are desired, the following references provide a detailed description of the preparation 10 of vinyl chloride plastisols which are suitable for use in the present invention: Plastisols and Organosols, edited by Harold A. Sarvetnick, 12 published by Van Nostrand Reinhold, 1972 and "PVC: Formulation, Compounds and Processing, A Review and Update", reprint of the Society 14 of Plastic Engineers, 1981.
The second principle component of the claimed curable 16 compositions is a copolymer of an aliphatic olefinically unsaturated material and an anhydride containing material.
18 The aliphatic olefinically unsaturated material can be a linear aliphatic material such as a polydiene. Suitable dienes 20 include polymers of 1,3-dienes containing from 4 to 12 and preferably from 4 to 6 carbon atoms. Typical dienes include 1,3-butadiene, 22 2,3-dimethyl-1,3-butadiene, isoprene, chloroprene, piperylene and ethylene propylene diene. Other polymerizable monomers such as methyl 24 methacrylate, acrylic acid and styrene can be copolymerized with the dienes.
26 The aliphatic olefinically unsaturated material can also be a normal alpha olefin such as l-decene, l-hexene, l-octene or 28 tetradecene.
The aliphatic olefinically unsaturated material can also be 30 cyclic or alicyclic such as pinene, indene or coumarene. Preferably the normal alpha olefin l-decene is utilized.
32 The anhydride containing material can be selected from a variety of materials which are capable of vinyl addition 34 polymerization. Suitable anhydrides include maleic anhydride, _ 4 _ 203553~

itaconic anhydride, citraconic anhydride, dodecenyl succinic anhydride 2 and nadic anhydride. Preferably, the anhydride containing material 1s maleic anhydride.
4 It should be understood that the scope of the anhydride cont~n~ng material is also intended to include simple adducts of an 6 anhydride, such as those mentioned above, with another suitable material capable of forming an adduct, such as rosin, the anhydride 8 adduct being copolymerizable with the aliphatic olefinically unsaturated material.
Generally, the copolymer of the present invention has a number average molecular weight ranging from about 500 to about 12 50,000, usually about 1000 to about 10,000 and preferably about 1000 to about 5000 as determined by gel permeation chromatography (GPC) 14 using a polystyrene standard.
It should be understood that in some embodiments, the 16 copolymer can be commercially obtained. For example, Colorado Specialty Chemicals provides RICON~131/MA-17 which is a copolymer of 18 polybutadiene and maleic anhydrlde.
The copolymer can be prepared by methods well known to those 20 skilled in the art. Briefly, excess olefinically unsaturated material and anhydride are free radically polymerized at 120~C to 180~C in the 22 presence of peroxide initiator to produce a 1/1 copolymer. Residual olefinically unsaturated material is stripped and the copolymer 24 supplied in flake form or dissolved in a suitable plasticizer.
Additionally, the anhydride can be added at temperatures exceeding 26 130~C to preformed polymers cont~n~ng olefinic unsaturation to yleld copoly~ers which are also useful.
28 The copolymer is typically present in the claimed composition in an amount ranging from about 0.5 to about 20, preferably from about 30 1 to about 5, the percentages based on the total weight of the composition.
32 The polyvinyl chloride plastisol is typically present in the claimed composition in an amount ranging from about 15 percent to 34 about 50 percent, preferably from about 20 percent the about 40 percent, the percentages based on the total weight of the composition.
*Txade mark ~ - ~ 5 ~ 203SS38 The compositions of the claimed invention can also contain 2 other resinous ingredients so long as they do not detract from the properties of the final composition. Examples of such resinous 4 additives include copolymers of polyvinyl chloride and polyvinyl acetate, copolymers 6 of styrene, butadiene, and/or butadiene-acrylonitrile or polybutadiene.
The claimed compositions can also contain a variety of 8 well-known and conventionally utilized additives, including fillers such as carbon black and bentonite clay, plasticizers, adhesion 10 promoters, stabilizers for the vinyl chloride polymer and antioxidants for the other polymer components. The compositions are generally 12 prepared by simply combining the various ingredients with agitation.
The claimed compositions are particularly suitable for use as 14 adhesives and sealants, preferably sealants, over primed metal. They can also be utilized over other substrates including cold rolled 16 steel, zincrometal and galvanized metal. The time and temperature for fusion can vary widely depending on the particular copolymer 18 composition and plasticizer. The compositions are usually fused by baking at a temperature of from about 120~C to about 180~C, preferably 20 from about 120~C to about 160~C. The time required for fusion of the composition usually ranges from about 20 minutes to about 120 minutes, 22 preferably from about 30 minutes to about 60 minutes.
The claimed compositions are particularly advantageous in 24 that they have excellent adhesion to primed metal substrates and in addition can be topcoated with a variety of coating compositions 26 without yellowing of the topcoat. The claimed compositions also exhibit good tensile strength and elongation, good reverse impact 28 resistance at low temperatures, e.g., -20~C and very good adhesion after condensing humidity exposure.
The following examples are illustrative of the invention and are not intended to be limiting.

- -Example 1 2 The following liquids were mixed together: 7.9g PLASTHALL DOZ
(dioctyl azelate from CP Hall), l.lg SYNPRON*431 (organophosphite 4 stabilizer from Synthetlc Products Co.), 24.4g diisodecyl phthalate (DIDP). The following solids were added to the mix under agitation:
6 15.9g VESTOLITE*E-7012 (polyvinyl chloride homopolymer from Huls), 5.6g OXY 567*(polyvlnyl chloride homopolymer from Occidental), 2.8g 8 OXY 6338 (copolymer of 95 wt.% polyvinyl chloride and 570 polyvinyl acetate from Occidental), 16.9g SNOWFLAKE*(calcium carbonate from 10 Thompson-Weinman), 19.8g MULTIFLEX SC (stearic acid coated calcium carbonate from Pfi~er) and 1.7g calcium oxide. This system was the 12 control with no adhesion promoter and no yellowing preventative. To test for yellowing resistance, a wedge of sealant was drawn down over 14 a 4" x 12" x .030" (10.16 cm x 30.48 cm x 0.08 cm) metal panel coated with ED3150 UNI-PRIME electrocoat primer commercially available from 16 PPG Industries, Inc. The primer had previously been fully cured at 350~F(177~C)/30 minutes. The wedge had the following dimensions:
~ ~ direction of drawdown:
18 ~ ~ 2 - 3 inches long taper to i~ 0.25 inch zero thickness ~ 2 inches ~~~~r 22 The sealant was then baked 30 minutes at 325~F(163~C). After cooling, the sealant and panel were topcoated, first with 1.5 mils (wet) of 24 white basecoat, UBC 8554 available from PPG Industries, Inc. followed, after a 2 minute flash time at room temperature, by 1.5 mils (wet) of 26 clearcoat, URC lOOa, also from PPG Industries, Inc. The painted panel was thcn baked 30 minutes at 250~F(121~C). To test for adhesion, a 28 knife blade was inserted under both thin and thick portions of the fully painted and baked sealant. To pass, failure needed to be 30 cohesive. The sealant could not pull cleanly off the primer at either thick or thin edges of the drawdown. Results are shown in Table 1.
32 To test for resistance to topcoat yellowing, the fully painted and baked sealant-plus-panel was placed in condensing, e.g. 100 percent 34 humidity cabinet at 130~F(54~C) for 1 week. Upon removal~ the panel was dried and vlsually inspected for color difference between topcoat *Trade mark B¦ -over the sealant and topcoat over the electrocoat primer. The visual 2 color difference was rated between 10 (greatest difference) and 0 (no difference). To pass the test, color difference needed to be less 4 than 2. Results are also shown in Table 1. A second method for determining color difference invol~red photomertic measurement with a 6 Macbeth Color Eye 2020 Plus*with a computer screen (Tandem 6AT/40, 6 HC) and appropriate software ("Color 2" from Davidson Colleagues, 8 Tatamy, PA 18085). The color difference was designated "~Y" and defined as follows:

aY - [Yellowness Index value 12 of topcoated sealant] - [Yellowness Index value of same topcoated panel without sealant]

16 Six readings per sample were taken and averaged for the l~Y value. A
detailed description of the yellowness index can be found in ASTM
18 method 6131, September 1, 1965. l~Y values are also shown in Table 1.
To pass the test ~Y needed to be less than 5. With no adhesion 20 promoter and no yellowing preventative, Example 1 showed no adhesion and severe yellowing.

Example 2 24The ingredients for this example are listed in Table 1. The procedure for mixing wa~ the same as for Example 1. This example 26 shows the effect of adding a commonly used adhesion promoter, such as EURETE~ 580, a polyaminoamide from Sherex Corporation. Adhesion was 28 acceptable, but topcoat yellowing resistance was poor.

Example 3 The ingredients for this example are listed in Table 1. The 32 procedure for mixing was the same as for Example 1. Copolymer A was a 12.5% solution of VMCA (copolymer of 81% vinyl chloride, 17% vinyl 34 acetate and 2% maleic acid from Union Carbide) in diisodecylphthalate (DIDP) and demonstrates the effect of an acid-modified polyvinyl 36 chloride/polyvinyl acetate used in place of polyaminoamide as an *Trade mark 203~i538 adhesion promoter. Adhesion was acceptable. Topcoat yellowing 2 resistance was improved, but 6till only fair. The solution was made by blending VMCA with DIDP on an air-mixer for one hour at 300~F.

Example 4 6 The ingredients for this example are listed in Table 1. The procedure for mixing was the same as for Example 1. Copolymer B was a 8 12.5% solution of VROH (copolymer of 93.1% vinyl chloride, 4.6% vinyl acetate and 2.3% vinyl alcohol from Union Carbide) in DIDP made by 10 blending VROH with DIDP on an air-mixer for one hour at 300~F. The example demonstrates the effect of a hydroxyl-modified polyvinyl 12 chloride/polyvinyl acetate used in place of polyaminoamide as an adhesion promoter. Adhesion was acceptable. Topcoat yellowing 14 resistance was improved, but still only fair.

16 Example 5 The ingredients for this example are listed in Table 1. The 18 procedure for mixing was the same as for Example 1. Copolymer C was the reaction product of l-decene and citraconic anhydride prepared as 20 described below. The example demonstrates the effect of an alpha-olefin/unsaturated anhydride copolymer on topcoat yellowing 22 resistance, which has improved to excellent. Note that in this formula, no adhesion to electrocoat primer was observed.

Reaction of l-Decene and Citraconic Anhydride 26 To a 5 liter round bottom flask fitted with a stirrer, thermometer, condenser, and two additional funnels was charged 2520 g 28 (18 moles) of l-decene. The l-decene was agitated under a N2 blanket and heated to 120~C. To the heated l-decene was added in separate 30 streams an initiator solution of t-butylperbenzoate (78.4g) in 280g of l-decene and a charge of 224g (2 moles) of citraconic anhydride. The 32 initiator feed was started 15 minutes before the citraconic anhydride feed and extended over 2 hours. The citraconic anhydride was added 34 over 1 1/2 hours. After both feeds were completed the entire solution _ ~ _ 9 _ was heated at 120~C for 1 hour after which it was heated to 180CC and 2 solvent removed. At 180~C the solution was 6parged with N2 for 1 hour then poured into a container. The resulting polymer had a Z7(-) 4 Gardner Holt Visco6ity, a color of 2 and a weight per gallon of 8.15, the solid6 at the end of a bake of 110~C for 1 hour were 98%.

Example 6 8 The ingredients for thi6 example are li6ted in Table 1. The procedure for mixing was the same as for Example 1. Thi6 example 10 demon6trate6 the improv~ t in electrocoat primer adhe6ion with the addition of Copolymer A (see Example 3) to Example 5. Note that 12 topcoat yellowing resistance was still excellent.

14 Example 7 The ingredients for this example are listed in Table 1. The 16 procedure for mixing was the same as for Example 1. Copolymer D was a 25% solution in DIDP of the reaction product of l-octene and maleic 18 anhydride prepared a6 de6cribed below. The polymer was used in combination with Copolymer A (see Example 3) and demonstrates another 20 alpha-olefin/unsaturated anhydride combination giving excellent topcoat yellowing resistance.

Reaction of l-Octene and Maleic Anhydride 24 To a 12 liter round bottom fla6k fitted with a stirrer, condenser, thermometer, and two dropping funnels wa6 added 3024g (27 moles) of 26 l-octene. The l-octene wa6 agitated under N2 and heated to reflux.
To the-refluxing l-octene was added in separate streams an initiator 28 18.23g of t-amyl peracetate 60% in odorless mineral spirit6 (LUPERSOL
555-M60 from Penwalt Corporation) di6601ved in 750 ml of butyl 30 acetate. The initiator 601ution was added over 3 hours total and it was started 1/2 hour before adding a 601ution of 1323g (13.5 moles) of 32 maleic anhydride di6solved in butyl acetate over two hours. When the additions were complete the solution was refluxed for 1 hour then it 34 was heated to 180~C and di6tillate was removed. On reaching 180~C the 601ution was N2 sparged for 1/2 hour and then poured into a pan. The 36 solid polymer was 97% solids at the end of a 110~ bake for 1 hour.
*Trade mark .

Example 8 2The ingredients for this example are listed in Table 1. The procedure for mixing is the same as for Example 1. Copolymer E was a 4 25% solution in DIDP of the reaction product of l-decene and maleic anhydride prepared as described below. Copolymer F was an 11.4%
6 solution of CHEMIG ~ P-83 (copolymer of 33% acrylonitrile, 63%
butadiene and 4% divinylbenzene) in DIDP, added to improve sealant 8 elongation. This example demonstrates the use of an alpha-olefin/
unsaturated anhydride copolymer as both adhesion promoter and topcoat 10 yellowing preventative. Adhesion is acceptable. Yellowing resistance is excellent.

Reaction of l-Decene and Maleic Anhydride 14To a 5 liter round bottom flask fitted with a stirrer, thermometer, condenser (continual take off type), and 2 addition 16 funnels was added 1403.5g (10 mole6) of l-decene. The l-decene was agitated and heated to 145~C. To this was added both an initiator, 18 33.8g of t-amyl peracetate 60% active in mineral spirits (LUPERSOL
555-M60 from Pennwalt Corporation) in 278.5g of butyl acetate and 20 491.2g of maleic anhydride (5 moles) dissolved in 1228g of butyl acetate. The initiator was started 1/2 hour before the anhydride 22 solution and the initiator solution was added over 3 hours while the maleic anhydride solution was added over 2 hours. After the additions 24 were complete the solution was held at 145~C for 1 hour then heated to 180~C and distillate removed the resulting material was N2 sparged for 26 1 hour at 180~C and then poured into a pan. The crystaline polymer was 98.4% solids as determined by heating a sample at 110~C for 1 hour.

Example 9 30The ingredients for this example are listed in Table 1. The procedure for mixing is the same as for Example 1. Ricon 131/MA-17 32 was a copolymer of 83% butadiene and 17% maleic anhydride from Colorado Specialty Chemicals. This example demonstrates the use of 34 another unsaturated aliphatic monomer/un6aturated anhydride combination giving acceptable adhesion and excellent topcoat yellowing resistance.

*Trade mark - 11 203553,~

Examples 1-9 plus 4 test results Liquids *
10 PLASTHALL DOZ 7.9 7.9 7.9 7.9 7.9 7.9 7.9 DIDP 24.4 24.4 11.2 11.2 24.4 11.2 6.5 25.6 39.7 12 Copolymer C . . . . 1.9 1.9 Copolymer E . . . . . . . 7.4 14 Copolymer D . . . . . . 7.5 SYNPRON*431 1.1 1.1 1.1 1.1 1.1 1.1 1.1 1.2 1.1 16 EURETEK*580 . .4 Copolymer A . . 15.1 . . 15.1 15.1 18 Copolymer B . . . 15.1 Copolymer F . . . . . . . 19.1 9.5 RICON*131/MA-17 . . . . . . . . 3.7 Solids 22 VESTOLITE*E-7012 15.9 15.9 15.9 15.9 15.9 15.9 15.9 15.9 15.9 OXY 567* 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 24 OXY 6338* 2.8 2.8 2.8 2.8 2.8 2.8 2.8 2.8 2.8 SNOWFLAKE* 16.9 16.9 16.9 16.9 16.9 16.9 16.9 20.6 20.6 26 MULTIFLEX*SC 19.8 19.8 19.8 19.8 19.8 19.8 19.8 17.5 24.1 Calcium Oxide 1.7 1.7 1.7 1.7 1.7 1.7 1.7 8.3 8.2 28 CABOSIL*TS-720 . . . . . . . .7 1.1 30 Adhesion FAIL ¦______PASS ¦ FAIL ¦ PASS
32 Yellowing Resistance Visual 4 6 3 3 0 0 0 0 34 ~Y 9.2 10.1 5.1 Not Run 1.3 1.2 2.3 Not Run *Trade mark

Claims (8)

1. A process for coating a substrate having an electrodeposited coating composition, comprising, (a) applying to said electrodeposited coating composition a plastisol based composition, comprising a polyvinyl chloride plastisol and between about 0.5 and about 20 weight percent based on total weight of the plastisol based composition of a copolymer of a cyclic-aliphatic olefinically unsaturated monomer material or an aliphatic olefinically unsaturated monomer material selected from the group consisting of alpha-olefins and dienes and an anhydride containing monomer material capable of vinyl addition polymerization; and (b) applying a topcoat over said plastisol based composition.

2. The process of claim 1 wherein the olefinically unsaturated material is selected from linear aliphatic and cyclic-aliphatic olefinically unsaturated material.

3. The process of claim 2 wherein the olefinically unsaturated material is a linear aliphatic material.

4. The process of claim 3 wherein the linear aliphatic material is a normal alpha-olefin.

5. The process of claim 4 wherein the normal alpha-olefin is 1-decene.

6. The process of claim 4 wherein the normal alpha-olefin is 1-octene.

7. The process of claim 1 wherein the anhydride containing material is maleic anhydride.

8. The process of claim 1 wherein the polyvinyl chloride is a mixture of functional polyvinyl chloride in which the functional groups are selected from hydroxyl, carboxyl or anhydride and non-functional polyvinyl chloride.