SE446307B - PROCEDURE FOR IMPROVEMENT OF FRAGADHESION TO A SURFACE OF POLYOLEFINE WHICH IS COATED WITH CHLORED POLYPROPEN AND EXPOSED TO UV RADIATION - Google Patents

Description

2 8003636-8 2 blisters or detachment, this lot is not acceptable to both the vehicle manufacturer and the vehicle owner. Accordingly, there is a great need in the industry for a primer that can provide good adhesion of dry and wet paint to surfaces or articles made from a polyolefin or polyolefin blend in which polyethylene or polypropylene is the sole or predominant polymer.

The present invention relates to a process for improving the adhesion of paint to a surface of articles made of polyolefin consisting of: (1) polyethylene, polypropylene or crystalline dipolymers of ethylene and propylene; (2) mixtures of at least two of those specified in group (1) above; or (3) mixtures of at least one of those specified in group (1) above with at least one elastomer consisting of ethylene / propylene dipolymers or EPDM copolymers wherein the total amount of polymer elastomers is not more than 50% by weight of the final the polymer blend; characterized by (a) cleaning the surface; (b) applying a thin layer of a chlorinated polypropylene to the coated surface, and (c) exposing the chlorinated polypropylene coated surface to ultraviolet radiation. The polyolefins to which the surface modification process according to the invention can be applied are well known in the art and are commercially readily available from one or more sources. There is an extensive patent literature describing processes for producing both high and low density polyethylene; isotactic * and syndiotactic polypropylene; both crystalline and elastomeric ethylene / propylene dipolymer; and KPDM copolymers; both tri- and tetra-polymers. These patents are well known in polymer chemistry.

Preferred crystalline etc / propylene dipolymers are hard, impact resistant types, which contain up to 2% by weight of ethylene. Preferred ethylene / propone copolymer elastomers contain about 30-75% ethone, 60-90% propylene and 0-10% non-conjugated diene or dienes.

These copolymers are rubbery and substantially amorphous. Non-conjugated dienes exhibit only one polymerizable double bond, which may be copolymerized with ethylene and propylene to EPDM copolymers having about 6-22 carbon atoms and include, for example, acyclic dienes such as 1,4-hexadiene, 1,9-octadiene, -ethyl-1,11-tridecadiene, 9-ethyl-1,9-undadiene, 8-ethyl-1,8-decadiene, 10-ethyl-1,9-dodecadiene, 12-ethyl-1,2-tetradecadiene , 13-butyl-1,1Z-heptadecadiene and 15-ethyl-1,15-heptadecadiene; and cyclic dienes such as dicyclopentadiene, 5-butenyl-2-norbornene, ethylidene-2-norbornene, S-methylene-l-norbornene, Z-ethyl-Z, 5-norbornadiene and 1, Preferred diene of this category is 1,4-hexadiene Representative non-conjugated dienes in which both double bonds are polymerizable are 1,5-hexadiene, 1,4-pentadiene and 2,5-norbornadiene 7 Vulcanizable homopolymers and copolymers is normally vulcanized before the surface modification process of the invention is carried out.

Vulcanization processes are well known in the art. For example, amorphous polyethylene, polypropylene and ethylene / propylene dipolymers are vulcanized with conventional peroxide systems. The EPDM copolymers, whether tripolymers or tetrapolymers, can be vulcanized either with a peroxide or with sulfur by methods well known in the art. Crystalline polyethone and polypropylene are not normally vulcanized.

The chlorinated polypropylene preferred in the process of the invention has an average molecular weight of about 5000-50,000 and contains about 5-ZS% by weight of chlorine. Commercially available chlorinated polypropylenes are sold by Eastman Chemical Products, Inc., Rochester, New York, under the designation CP-343-1 and CP-515-2 and may be suitably used in the present process. The former of these two commercial products consists of a chlorinated polypropylene which is presumed to contain cyclic anhydride groups in the polymer chain and has an average molecular weight of about 15,000. Its chlorine content is about 15% by weight. The other commercial material has approximately the same molecular weight and chlorine content but does not contain any cyclic anhydride groups in its main chain. Chlorinated polypropylene can be easily prepared by polymer chlorination in solution, melt or solid phase at moderate to high temperature according to well known techniques as described, for example, in Raff and Doak, "Crystalline Olefin Polymers 11," page 239, Inter-. Publishers, New York, NY, 1964, In practical use of the chlorinated polypropylene science, it is preferred to use a solution of the chlorinated polypropylene in a suitable solvent, for example an aromatic hydrocarbon, Alicyclic hydrocarbons may be used in solvent mixtures and a chlorinated hydrocarbon. or a solvent landing. due to their low toxicity and low cost availability. Tetrahydrofuran can also be used. Suitable alicyclic hydrocarbon diluents include cyclohexane and methylcyclohexane. Although chlorinated hydrocarbons, both as aliphatic TO 40 gsoosszs-s 4 and aromatic, can be used, these are not preferred due to their higher toxicity. The concentration of the chlorinated pellet propylene in the solution may be about 0.1-5.0. weight percent but 1.0-2.5% is preferred.

The polyolophine surface to be treated according to the process of the invention must be thoroughly cleaned. Cleaning can be accomplished by scrubbing with water and soap or detergent or by solvent cleaning with, for example, a hydrocarbon, a chlorinated hydrocarbon, a ketone or any other suitable solvent. The cleaned surface is then allowed to dry, possibly at an elevated temperature. A solution of chlorinated polypropylene is then applied to the clean surface and the solvent is allowed to evaporate, possibly again at elevated temperature. Finally, the primed surface is exposed to ultraviolet radiation.

Most commercial sources of ultraviolet radiation can be used in the process of the invention, although the most effective radiation is obtained in the wavelength range of about 200-40 ° nm. preferably the radiation exposure time is adjusted so that the radiation sonication received by the surface is about 0.10-1.0 J / cm 2. Optimal radiation energy range is 0.2-0.5 J / cmz.

The surface that has been primed with chlorinated polypropylene and irradiated with UV radiation is now ready for painting. The quality of the color adhesion can be determined in tests for both dry and wet adhesion as explained in the following examples.

The polyolefins and polyolefin mixtures which can be advantageously treated by the process according to the invention can be either unmixed or mixed in a conventional manner, for example with carbon black and other fillers, processing oils, plasticizers and similar constituents. However, the proportions of individual polyolefins in the blends stated previously are based on the polyolefins themselves and not on the weight of a blended polyolefin composition.

The present invention is further illustrated by the following oxamples in which certain preferred embodiments thereof are described and in which all parts, proportions and percentages are by weight unless otherwise indicated. The polymer melt flow rate is then determined according to ASTM D-1238-73 phytingclsc L): ÉšEEEEl_l A filler-containing polyolefin composition forward- CF! 40 s 80Û3628 ~ 8 was set by mixing the following ingredients in an internal mixer for two minutes at TSOOC. 2213: EPDM rubber (1) 31.7 Polypropylene (Z) 38.7 HAF-black 29.6 '(1) Non-crystalline copolymer of medium viscosity of 35.5 mol% propylene / 63 mol% ethylene / 1.5 mole percent 1,4-hexadiene having a Mooney viscosity (ML1 + 4) of 39 at 120 ° C. (2) Homopolypropylene with a melt flow range of 10-12.

Sheets of this thermoplastic composition were injection molded at ZSZOC. Two discs were cleaned in a powder wash cycle and primed as follows: On both discs, the primer consisted of a light spray coating of a 1% toluene solution of chlorinated polypropylene (CP-343-1, Eastman Chemical Products Inc.).

The weight of chlorinated polypropylene on a dry basis deposited on each disk was 0.095 mg / cm 2. After the priming had been carried out and the boards had been allowed to dry, one of the two boards was also exposed to UV radiation from a quartz jacketed mercury meadow lamp of medium pressure with a irradiation power of about 80 W / cm lamp length. The exposure ring was regulated so that the disk absorbed all the radiation that accompanied an irradiation of 0.35 J / cm 2 at a wavelength of 365 nm. The second disc did not receive any UV radiation. Both discs were then painted with a flexible E (100, PPG Industries) to give an alkyd enamel paint (Durethane dry film thickness of 22 microns.) The enamel was fired for 40 minutes at 120 ° C.

The boards were tested as follows: Li) Dry adhesion. A grid pattern of notches was performed through the paint over a small test area of the sample. The grid pattern consisted of a series of parallel notches at a distance of about 1.5 mm containing two sets of notches perpendicular to each other and a third set diagonally to the first two. Reinforced adhesive tape was then pressed into the paint over the surface of the checkerboard inserts and then quickly torn off. The adhesion was assessed in values of from 100 to 0% depending on the color surface left by the adhesive substrate. íiilnyëtmadbesion. In the center of the disc nndstudes. an X.

The disc was then placed about S cm mnkr odii a1vhnæl of 450 against the nozzle to a river generator so that the nozzle which could still give wet steam at a pressure of about 0.4 MPa overpressure was directed towards the * center of said X. The test consisted of measuring the time it took for the vapor beam to initiate lack of color wide adhesion in the center of the X and was performed for a maximum of 180 seconds. This test is particularly useful for evaluating the ability of colored sections on the outside of vehicles to withstand exposure to an automatic car wash. The following results were obtained: Without UV With UV Dry udhesíon 90% I 100% Wet udhesion 10 s> 180 s Exemgel 2.

Sheets were prepared and tested as in Example 1 except that the following thermoplastic composition was used: U Parts Erna rubber Ü) so 7 Polypropylene (Z) - 50 (1) Partial crystalline copolymer of 18 mole percent propylene / 81 mole percent ethylene / 1 mole percent 1,44hexadiene with a Mooney viscosity: (L-ILZHU) decrease at 121%. (2) Same as in Example 1. - Results: In Uiggmgy With Uv Dry adhesion 95.% n 100% Wet adhesion 50 s> 180 s ššsaasiš - Discs were prepared and tested as in Example 1 except that the following thermoplastic composition was used; 'Arrows Propylene homopolymer (1) 99 HAP black _ 1 (1) Melt flow value 4.

The following test results were obtained: "Without UV With UV Dry adhesion 10% 10% Wet adhesion 10 s 20 s Excmgel 4.

Discs were prepared as tested as in Example 1 except that the discs were fired for 3 hours at 10S ° C and that the following composition was used: 40 ä 8003628-8 29111: EFDM rubber from Example 2 20 'High density polyethylene 80 (melt index 2.8) The following test results received: Utezull! Dry adhesion 99% Wet adhesion 180 s This example compared the use of two different commercial chlorinated polypropylenes, namely UP-343-1 and CP ~ 515 ~ Z, both provided by Eastman Chemical Products, Inc.

Sheets having the same composition as described in Example 1 were cleaned in a wash cycle and then lightly spray coated with one or the other of the two chlorinated polypropylenes as 1% solutions in toluene. After drying, the discs were exposed to UV radiation as described in Example 1.

Two coatings of flexible alkyd paint were applied: about 18 microns of a neutral gray base coat, which was fired for 30 minutes at 11590, and about 45 microns of a white coating, which was fired for 40 minutes at 115 DEGC.

The following test results were obtained: CP-343-1 Chlorinated polypropylene CP-515-2 Deposited weight, mg / cm ”0.09 _0.10 Dry adhesion [al 100% 100% Dry adhesion (including very good good Wet adhesion (Q)> 60 s> 60 s Dry adhesion (d) Acceptable Acceptable (a) As described in Example 1. (b) A V-shaped cut was made through the paint and the paint was peeled off backwards from the tip of this V with a sharp knife. qualitative estimate of the force required for peeling the paint.

(C) As described in Example 1. The test was stopped after 60 seconds. (d) The painted board with an X cut in the paint surface was immersed in distilled water for 10 days at 3300. After removing the water, the board was quickly dried and a reinforced pressure sensitive tape was pressed over the center of the X slot. The tape was then quickly torn off. "Acceptable" indicates that no paint was removed.

It is obvious that both types of chlorinated polypropylene gave acceptable levels of adhesion.

Comparative examples using benzophenone and UV radiation as described in Canadian Patent Specification 974,928.

Examples 1-3 above were repeated, but instead of using a chlorinated polypropylene primer, the primer was carried out by spraying the disk with a 5% solution of benzophenone in pretoleum naphtha with a boiling point of 120 DEG-140 DEG C. (dry weight of the deposit 0.056 mg / cm 2). ; after the solvent had evaporated, the sprayed surfaces were exposed to UV irradiation (approximately 0.5 J / cm 2 measured at a wavelength of 365 nml. Then, paint was applied using the same color type, thickness of dry film and color firing cycle as in the above example. The following results were obtained: In 4 Polyolefin composition and type Dry Wet as in the above example adhesion,% adhesion, s 1 30> 180 2 0> 180 3 o 0 <5 _ Comparing these results with the results of Examples 1-3 shows the treatment with chlorinated polypropylene primer due to ultraviolet radiation is more effective than benzenephenone treatment due to ultraviolet radiation.The improvement is especially great for polypropylene mixtures with EPDM rubber but also for polypropylene alone an improvement and comparison is achieved. UV radiation as described in U.S. Patent No. 3,619,245.

Additional discs identical to those used in Example Z above were primed with trichloroethene and exposed to UV as described in U.S. Pat. No. 3,619,246.

After the yiun of a slice had been cleaned ~ in a washing machine * and dried in an oven, the trichloroctene was cured on the surface. A short time later (for example 1-2 minutes) the surface was exposed to UV radiation of 0.5 J / amg at a wavelength of 365 nm. Data obtained only from the UV lamp manufacturer (Hnnovia Lamp Division, Canrad Precision Industries) indicate that 0.5 J / cm at 365 nm is equivalent to an exposure of approximately 1.43 J / cmi in the range 240-400 nm. This is within the irradiation range indicated in the examples of U.S. Pat. No. 3,619,246. A color scheme described in Example 3 above is described above.

I "-¿. '\ L_i: u1 151' ~ * 1 <1J1f = i_9_fæ §ï =." 1.1í.; _ §1.sl! 19f§ fax: IIU T.> 1SU s It is obvious that the degree of The dry adhesion obtained with this primer is considerably lower than that obtained with the chloropropylene / UV primer of the present invention.

Claims (9)

19 8003628-8 A method for improving color adhesion to a surface of an article made of polyolefin, which consists of (1) polyctone, polypropylene or crystalline dipolymers of ethylene and propylene; (2) mixtures of at least two of those listed in (1) above; or (3) mixtures of at least one of the above in (1) with at least one elastomer consisting of ethylene / propylene dipolymers or EPDM copolymers, wherein the total amount of polymer elastomers is at most about 50% by weight of the final the polymer blend; k ä n n e t e c k n a t of Ca) cleaning the surface; (b) applying to the cleaned surface a thin layer of chlorinated polypropylene; and (e) exposure of the surface coated with chlorinated polypropylene for ultraviolet radiation. The method according to claim 1, characterized in that the chlorinated polypropylene has a molecular weight of about * SOOG-50,000 and contains about 5-25% by weight of chlorine. 3. A process according to claim 2, characterized in that the chlorinated polypropylene contains cyclic anhydride groups in the polymer backbone. 4. A method according to claim 2, characterized in that the ultraviolet radiation has a wavelength of about 200-400 nm. ' 5. A method according to claim 4, characterized in that the energy of the ultraviolet radiation received by the surface of the polyolefin article is about 0.1-1.0 J / cm 2. 6. A method according to claim 5, characterized in that the energy of ultraviolet radiation received by the surface of the polyolefin article is about 0.2-0.5 J / cm 2. 7. A process according to claim 1, characterized in that the polyolefin is a crystalline, impact-resistant, hard ethylene / propylene polymer. 8. A process according to claim 1, characterized in that the polyolefin is a mixture of polypropylene with an EPDM copolymer. f 9. A process according to claim 1, characterized in that the polyolefin is a mixture of a crystalline, impact-resistant hard ethylene / propylene dipolymer with an elastomer.