PRIMER FOR PRODUCING A PARTABLE ADHESIVE BOND

Abstract

Primer for producing a partable adhesive bond, the primer being based on a pressure-sensitive adhesive which comprises a chemical or physical blowing agent.

Claims

1. A primer for producing a partable adhesive bond, the primer being based on a pressure-sensitive adhesive which comprises a chemical or physical blowing agent.

2. The primer according to claim 1, wherein the pressure-sensitive adhesive of the primer is based on acrylates.

3. The primer according to claim 1, wherein the pressure-sensitive adhesive of the primer comprises a copolymer based on acrylic esters, preferably a copolymer of at least one acrylic ester with vinylcaprolactam.

4. The primer according to claim 1, wherein the pressure-sensitive adhesive of the primer is free from acrylic acid.

5. The primer according to claim 1, wherein the blowing agent is a physical blowing agent.

6. A layered structure comprising a first component, a primer layer which is on the component, the primer being based on a pressure-sensitive adhesive, which comprises a chemical or physical blowing agent, and being applied from a liquid phase in a layer thickness (after drying) of not more than 30 μm, and an adhesive tape, which is connected via the primer layer to the first component.

7. The layered structure according to claim 6, wherein a second component is bonded on the free side of the adhesive tapes.

8. A method for parting a layered structure comprising, a first component, a primer layer which is applied on the component, the primer being based on a pressure-sensitive adhesive, which comprises a chemical or physical blowing agent, and being applied from a liquid phase in a layer thickness (after drying) at not more than 30 μm, a first adhesive tape, which is connected via the primer layer to the first component, the layered structure being heated until the blowing agent present in the primer expands, so that the peel adhesion of the primer layer is reduced to an extent such that the adhesive tape is removable from the component.

9. A method of producing a component for a motor vehicle, which comprises incorporating the layered structure according to claim 6 into said component.

10. A method of producing an electronic device or component for an electronic device, which comprises incorporating the layered structure according to claim 6 into said electronic device.

11. The primer according to claim 5, wherein the physical blowing agent is thermally expandable, thermoplastic microspheres.

12. The layered structure according to claim 6, wherein the adhesive tape is a pressure-sensitive adhesive tape.

13. A component for a motor vehicle, which comprises the layered structure according to claim 6.

14. An electronic device, which comprises the layered structure according claim 6.

15. A component for an electronic device, which comprises the layered structure according claim 6.

Description

EXAMPLES

[0149] Basis polymers for primers: [0150] pressure-sensitive adhesive for primer (PSA 1)

[0151] The PSA copolymer contained in the primer in accordance with the invention was produced using the following raw materials: [0152] 70 wt % n-butyl acrylate (CAS: 141-32-2) and [0153] 30 wt % vinylcaprolactam (CAS: 2235-00-9)

[0154] The copolymer was prepared in a manner known to the skilled person by means of radical polymerization in a solvent mixture of ethyl acetate/isopropyl alcohol (168/1). The copolymer has a K value of about 84 and is adjusted to a solids content (SC) of 30 wt %.

[0155] In the peel adhesion test, coated in a thickness of 25 μm onto etched PET film (36 μm), the copolymer exhibits a peel adhesion of 2.5 N/cm. It is therefore a pressure-sensitive adhesive.

Primer Polymer 2 for a Comparative Example

[0156] To produce the primer base of the comparative example, the thermoplastic copolyamide Platamid M 1276 (from Arkema) was dissolved in a solvent mixture of [0157] 60 wt % ethanol, [0158] 18 wt % isopropanol, [0159] 18 wt % methylcyclohexane and [0160] 4 wt % water

[0161] and adjusted to a solids content (SC) of 15 wt %.

Primer Formulation

[0162] For the production of the primers of the invention, the base polymers described above in terms of their preparation and composition were used, along with the following raw materials, solvents and blowing agents: [0163] Titanium tetraisopropoxide (Tyzor® TPT, Lehmann & Voß, CAS 546-68-9) [0164] Isopropyl alcohol (CAS 67-63-0) [0165] Microballoons from Matsumoto, type FN 100SSD [0166] (size: 6 to 11 μm, T.sub.start: 120 to 130° C., T.sub.max: 145 to 155° C.) [0167] Microballoons from Matsumoto, type FN 100 SD [0168] (size: 10 to 20 μm, T.sub.start: 125 to 135° C., T.sub.max: 150 to 160° C.)

[0169] To produce the primers according to the invention, the primer PSA 1, in addition to the solvents contained in the primer PSAs, was additionally diluted with isopropyl alcohol to a solids content (SC) of 10 wt %.

[0170] In all of the examples the solids contents were chosen in each case so as to enable sufficient layer formation, allowing the corresponding comparative experiments to be conducted.

[0171] The raw materials/components specified in the examples were mixed using a magnetic stirrer from IKA® and a magnetic stirring bath for about 20 minutes.

Example 1

Primer Composition:

[0172]

TABLE-US-00001 Raw material/component wt % Solution of primer PSA 1 (SC 10.0 wt %) 89.60 Tyzor TPT 0.40 Matsumoto FN 100 SSD 10.00

Example 2

Primer Composition:

[0173]

TABLE-US-00002 Raw material/component wt % Solution of primer 1 (SC 10.0 wt %) 89.60 Tyzor TPT 0.40 Matsumoto FN 100 SD 10.00

Primer Composition:

[0174]

TABLE-US-00003 Raw material/component wt % Solution of primer 1 (SC 10.0 wt %) 97.10 Tyzor TPT 0.40 Matsumoto FN 100 SD 2.5

Example 4 (Comparative Example)

Composition of Comparative Primer:

[0175]

TABLE-US-00004 Raw material/component wt % Solution of primer polymer 2 (SC 15.0 wt %) 90 Matsumoto FN 100 SSD 10

[0176] The specified solids contents of the respective polymers in solution can be used in each case for unambiguous determination of the weight fractions of microballoons relative to base polymers in the primer compositions.

Producing the Test Specimens

[0177] A layer with the primer of the invention is produced in manner known to the skilled person, by first applying (using knife-coating technology) the primer in a defined layer thickness on a substrate (steel plate). Thereafter the solvent or solvents can be evaporated, after which the test adhesive tape can be applied to the substrate, which now bears the dried primer in a layer thickness of 15 or 25 μm, respectively. The time elapsing between application and evaporation of the solvent and the application of the test adhesive tape may be just a few minutes, or else several days or weeks.

[0178] The test adhesive tape with which the primers were tested is based on a polyacrylate PSA. The tape in question is the acrylate foam adhesive tape Tesa® 75120.

[0179] Tesa® 75120 is a double-sided black adhesive tape which consists of a black acrylate foam providing high-level impact damping.

[0180] The thickness is 200 μm.

[0181] The peel adhesion on steel (initial) is 13 N/cm; the peel adhesion polycarbonate (initial) is 10.9 N/cm.

Activating the Blowing Agents

[0182] For the activation of the blowing agents, the test specimens were stored in an air circulation oven at 150° C. for 5 minutes. Activation of the blowing agents reduces the peel adhesion measured. After the thermal activation, the peel adhesion is measured at room temperature, preferably after a cooling time of 5 minutes.

[0183] Alternatively, if the substrate is a thermally conductive substrate, the blowing agents may also be activated by placing the test specimens on a precision hotplate (1 minute at 155° C.).

[0184] To characterize the specimens produced in accordance with the invention, peel adhesions were determined before and after activation in the air circulation heating oven. The results obtained in this determination were as follows:

TABLE-US-00005 Layer Before After activation Primer thickness activation (5 min, 150° C.) Example 1 15 μm  9.6 N/cm (A) 0.4 N/cm (A) Example 2 25 μm 10.1 N/cm (A) 0.6 N/cm (A) Example 3 25 μm 13.0 N/cm (A) 2.4 N/cm (A) Comparative 15 μm  9.0 N/cm (A) 2.6 N/cm (A) Example 4 None — 11.5 N/cm (A) 13.2 N/cm (A)  A = Adhesive detachment of the adhesive tape

[0185] Examples 1, 2 and 3 show clearly and unambiguously the effect of the primer of the invention in leading to a significantly greater reduction in the peel adhesion than the comparative primer, more particularly to a reduction of more than 75% in the peel adhesion.