Release coating and process

Abstract

A release coating having improved stability under aging conditions of heat and humidity is described whose release force can be altered by varying the amount of multi-lobe emulsion polymers relative to release agent.

Description

EXAMPLES

Release coatings were prepared from aqueous multi-lobe emulsion polymers having a multimodal particle size distribution and from conventional aqueous emulsion polymers as comparative examples, as summarized in Table 1.

TABLE 1
Polymer compostions used to prepare release coatings
				High Speed
				Adhesion to		High Shear
				Backing		Viscosity at
				(HSATB)		38% solids,
				X Increase		100000, S−1Cps.
		Polymer	Release	after aging	Strike	Measured
Example	Polymer Composition	Morphology	Additive	(ranges)	through	by Hecules
1	51.9BA/46.8MMA/1.3 AA	Multi-lobe	Aerosol	<1 X	None	15
			22 ™
2	51.9BA/46.8MMA/1.3 AA	Bimodal/	Aerosol	2-3 X	Slight	13
		Multi-lobe	22 ™
3	51.9BA/46.8MMA/1.3 AA	Bimodal/	Aerosol	2-3 X	Some	7
		Spherical	22 ™
4.	Commercial	Spherical		3-4 X	Some	Not tested
Rhoplex
R-308

TABLE 2
Tg impact on release
Polymer compostions used to prepare release coatings
Exam-	Polymer	Polymer	Release	Tg,
ple	Composition	Morphology	Additive	° C.	Release
1	51.9BA/46.8MMA/	Multi-lobe	Aerosol	15	Loose
	1.3 AA		22 ™
2	41.7BA/57.0MMA/	Multi-lobe	Aerosol	25	Medium
	1.3 AA		22 ™
3	37.8BA/60.9MMA/	Multi-lobe	Aerosol	35	Tight
	1.3 AA		22 ™

Examples 1-4 were Tested as Follows:

• Samples with 4.9% of the release additive Aersol 22™, commercially available from Cytec Industries Inc., were formulated into a polymer emulsion (solids on solids) and then the release coats prepared from Examples 1-4 were applied to the smooth side of the crepe backing (0.20m×0.25 m), using wire wound rod (WWR) # 0-5 to achieve coat weights between 6-8 g/m². The proper selection of the WWR # depended on solids content, rheology and crepe porosity for samples 1-4. The coated samples were placed in an oven for 30 seconds or 60 seconds @ 130° C.-190° C. (depending on the release chemistry). After drying, all samples were placed in CTR, controlled temperature room at 22° C. and 50% relative humidity, prior to testing. Duplicate samples were placed for a minimum of 24 hrs and a maximum of 1 week at 65° C. and 60-80% relative humidity.

In addition to standard release testing, samples were evaluated for strike-through, which is a qualitative measurement to the degree of bleed through for samples applied at low viscosity and solids. Typically, during the actual release coating application the coating experiences both shear and pressure. The combined shear and pressure during the coating, especially when the coating solids are reduced, causes the release coating to penetrate into the substrates, resulting in inconsistent coverage and therefore inconsistent unwind.

For testing release properties, 5 cm by 15 cm release coated samples were secured to a steel panel using double face tape. Any source of contamination from contacting the coated release was avoided. Approximately ten centimeters of the desired adhesive coated tape were applied to the release coating and pressed with a 2 kg rubber roller by rolling once in each direction. A minimum of 4 panels were prepared for each test, two panels for initial and two panels for aging. The strips were attached to Chemlnstruments' AR1000 high speed release tester, and each specimen was peeled at rate of 0.3 meter/second. Force/unit width was measured and compared before and after aging. Data were tabulated and percent increase was calculated and the results of which are shown in Table 1.

Claims

1. A release coating comprising: i) at least one aqueous multi-lobe emulsion polymer; andii) at least one release agent.

2. A method of making a coated product comprising: i) applying the release coating of claim 1 onto a substrate to form a coated product; andii) drying the coated product.

3. A method of altering the release force of a release coating comprising the steps of: (a) providing at least one aqueous multi-lobe emulsion polymer; and (b) varying the amount of at least one release agent relative to the amount of (a).

4. A method of altering the release force of a release coating comprising the steps of: (a) providing at least one aqueous multi-lobe emulsion polymer and at least one release agent wherein the release agent is provided in the range of 0.1-20%; and (b) varying the Tg of the at least one aqueous multi-lobe emulsion polymer.

5. The method of claim 4 wherein the Tg is in the range of 0° C. to 50° C.

6. The method of claim 4 wherein the Tg is in the range of 25° C. to 35° C.

7. The method of claim 4 wherein the particle size distribution is in the range of 50 nm to 10000 nm.

8. The method of claim 4 wherein the particle size distribution is in the range of 100 nm to 1000 nm.

9. The method of claim 4 wherein the release agent comprises a surfactant.

10. The method of claim 9 wherein the surfactant comprises a hydrocarbon hydrophobe of greater than ten carbons.