JP3034014B2 - High temperature resistant shape-flexible tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates generally to pressure-sensitive adhesive tapes. More particularly, the present invention relates to harness tapes for automobiles.

The present invention is an improvement over U.S. Patent Application No. 252,092, filed September 30, 1988 under the same inventor's name, and assigned to the assignee of the present invention. Said patent application is incorporated herein by reference. As mentioned in the above-mentioned patent application, such industrial adhesive tapes are impervious to liquids, chemically resistant, flame-retardant, non-corrosive, easy to tear in the lateral direction, and have flexibility. It is particularly desirable to have such characteristics. This shape flexibility is a particularly desirable property for use as an automotive harness tape where small objects must be tightly wrapped. According to the disclosure of said patent application, the backing layer comprises chlorinated polyethylene.

While the currently used industrial tapes have the above advantages, they also have some disadvantages.
One significant disadvantage is the lack of heat resistance. Commercially available tapes have optimal heat resistance at a temperature of 105 ° C.
Therefore, it cannot withstand a temperature higher than 105 ° C. for a long time. Furthermore, commercially available industrial tapes having good shape flexibility have poor heat resistance, and tapes having good heat resistance have poor shape flexibility. (Shape flexibility is subjectively defined as the capacity to wrap small objects, and objectively, cantilevered by the American Society for Testing and Materials (ASTM) 1338 (Cantilev
er) Characteristics defined by the method. Therefore, in the prior art, heat resistance and shape flexibility are mutually exclusive characteristics. Nevertheless, the industry, especially the automobile industry, still demands a harness tape having heat resistance and good shape flexibility. This requirement is particularly strong when harness tape is used to wrap small objects in the engine room. The tape lining of the prior art having good shape flexibility decomposes at high temperatures, whereas the tape lining of the prior art having high heat resistance is peeled off from the adhesive. Similarly, at high temperatures, the tackiness of the adhesive weakens and thus the bond strength is greatly reduced.

Accordingly, a main object of the present invention is to provide a pressure-sensitive adhesive tape having good shape flexibility and high heat resistance, which maintains the structural and functional integrity of the backing layer and the adhesive layer in a high temperature range exceeding 105 ° C. To respond to long-standing needs.

The object of the invention is fulfilled in a novel way of providing a chlorinated polymer backing layer provided with a pressure-sensitive adhesive layer on one surface (the backing layer and the adhesive layer are cross-linked).

A main object of the present invention is to provide a harness tape for automobiles having good shape flexibility that maintains functional and structural integrity up to 135 ° C. with respect to a normal use state in a case where a reinforcing scrim is used and a case where a reinforcing scrim is not used. Is to develop. Furthermore, as the automotive industry is moving toward higher engine operating temperatures, there is a particular need for heat resistant harness tapes. The characteristics of these tapes include shape flexibility,
Tensile strength, structure, barrier properties, adhesion and the like must also be maintained at elevated temperatures.

The novel flexible adhesive tape of the invention is characterized in that it comprises a crosslinkable chlorinated polymer backing layer provided with a crosslinkable pressure-sensitive adhesive layer on one surface; Wherein the backing layer has heat resistance; furthermore, the backing layer has good shape flexibility at high temperatures; and further, the adhesive layer is cross-linked, thereby shearing at high temperatures. The resistance to forces is greatly increased.

According to the invention, a preferred backing material consists essentially of a blend of polyethylene with 26-42% by weight of chlorine in the form of chlorinated polyethylene and 58-74% by weight of polyethylene in the form of chlorinated polyethylene. . Although not essential to the practice of the present invention, other components known per se (e.g., barium-cadmium, lead, or "Encyclopedia of Polymer Science") to perform a particular desired function Heat engineering agents such as other substances described in "And Engineering", pages 503 to 504; known antioxidants such as hindered amines; and coloring agents such as carbon black).

Suitable pressure-sensitive adhesives include acrylic adhesives and rubber-based adhesives known per se (for example, natural or synthetic rubber elastomers). Typical adhesives of this type include natural rubber, tackifiers,
And other drug blends that perform the particular function desired. Choosing the right adhesive, at least to some extent,
It depends on the type of support to which it adheres, but in any case it is up to individual choices based on the judgment of the skilled worker. However, in the present invention, the unwind propertie is used to maximize the unwinding, i.e., to counteract the effects of irradiation which would increase the adhesion to the backing layer (thus increasing the unwinding).
It should be noted that low s) adhesives are particularly preferred. Therefore, an adhesive having an unwinding property of up to 80 oz / in is preferable. The selection of a particular adhesive from those known in the art is not part of the present invention and need not be described in further detail.

Crosslinking may be performed by a chemical agent or by irradiation. Suitable crosslinkers include organic peroxides and amine accelerator / sulfur donor type systems, of which the representative is thiadiazole. The choice of chemical crosslinker will depend on the desired result. Thus, extra scorch safety, bin stability, low compression set, and 300-32
When heat aging resistance at 5 ° F is required, curing with a peroxide is preferred. However, when performing over a wide range of temperature and pressure conditions with less generation of volatile by-products than peroxides, curing with thiadiazole is preferred.

Irradiation (which is a preferred crosslinking method) can be performed by any known method, and typical methods among these are methods using γ-rays, α-rays, and preferably electron beams. Preferred doses range from about 5 to about 20 megarads (Mrads). Functionally, to provide heat resistance, a gel content of 40% by weight (% of insoluble material)
It is preferred to crosslink to a degree.

In other embodiments of the present invention, a tie coat may be incorporated if a more stable bond between the backing layer and the adhesive layer is required. The tie coat is chosen to provide good bonding with all of the tape support so that a laminate with the necessary stability is obtained without delamination or separation (including the adhesive layer). , Some of which are present in the scrim gap). Particularly useful materials for this purpose are polyolefin copolymers, especially polyethylene copolymers such as ethylene methyl acrylate, ethylene vinyl acetate, and ethylene acrylic acid. From the above description, other useful tie coat materials will be readily apparent to those skilled in the art.

In still other embodiments, the tape can be incorporated with a thrill to make the tape easier to tear. The scrim preferably comprises a woven fabric of synthetic fibers, preferably a woven fabric of polyester. However, the fibers need not all be synthetic, and the woven fabric preferably contains up to 50% cotton in the warp direction to increase finger tear uniformity without reducing flame retardancy. .

A preferred woven fabric is a transversely woven polyester pre-fired yarn (false) described in U.S. Pat. No. 4,303,724.
−twist yarn or woven yarn (texturized y)
arn). As previously mentioned,
The warp yarn may be, and is more preferably, a blend of cotton and polyester. For example, tapes made in accordance with the present invention using the woven fabric described in the aforementioned patent having a 75-25 polyester / cotton blend in the warp yarns provided satisfactory finger tear in the transverse direction. However, 50-50 polyester /
The use of the cotton warp blend also provided a slightly improved finger tearability. In each case, preferred fabrics include no more than 20 interwoven yarns per inch in the weft direction (false twisted yarns) and no more than 35 yarns per inch in the warp direction.

Accordingly, as used herein and in the claims, "woven fabric containing synthetic fibers" or "woven fabric containing polyester" means that the yarn in the weft direction is a synthetic fiber or polyester and the warp direction is At least 50% of the yarns are synthetic fibers or polyester [i.e.
Which may contain as many as 50% of other yarns (eg, cotton).

The manufacture of the novel tape of the present invention can be performed according to known methods such as calendering, extrusion, and electron beam irradiation, and thus does not form a part of the present invention.

The novel tape of the present invention manufactures each component individually,
It can be produced by subsequently coating the components. For example, the backing layer, the tie coat, and the scrim can be individually supplied by a coextrusion coating method known per se to form a laminated structure composed of these three components. Then, the adhesive layer can be coated on the cloth support by a known coating method (for example, calendering, casting, or extrusion). In embodiments that do not include a tie coat or scrim, not only the adhesive layer but also the backing layer can be obtained in a single calendaring operation.

The following examples are intended to illustrate the practice of the present invention, but do not limit the invention.

Example 1 0.25 on a fabric of 20 × 10 (96 filaments, 200 denier polyester yarns, 20 warp yarns per inch; and false twist yarns, 10 weft yarns per inch).
The tape was constructed by coextruding a tie coat consisting of .about.0.5 mil ethylene methyl acrylate; and a 2.0-2.5 mil film consisting of a chlorinated polyethylene blend containing 24% by weight of chlorine. Finally, a 1.5 mil thick adhesive rubber based adhesive layer was rolled onto the backing prepared above. The resulting tape was exposed to 10 Mrad through the backing.

Example 2 A 1.2-2.0 mil thick adhesive rubber-based adhesive layer was rolled onto a 5 mil chlorinated polyethylene sheet containing 24% by weight chlorine to polyethylene in a chlorinated polyethylene blend. Apply the resulting tape to the entire backing material for 10 minutes.
Exposed to Megarad.

The following table objectively illustrates the novel features of the present invention in the form of test data. Table I specifically illustrates a tape composition comprising a cloth scrim and a tie coat prepared as described in Example 1, exposed to 0 and 10 megarads. The tensile strength, elongation and adhesion to the backing were subsequently measured.

Table I Dose (Megarad) 0 10 Adhesion to steel 61 52 (oz / inch) Adhesion to backing 32 32 (oz / inch) Unwind speed 12 inches / min 35 74 (oz / inch) Unwind I 100 feet / Min 52> 300 (oz / in) The data presented in Table I show the effect of irradiation on adhesion to the backing at 2 inches / min.
Illustrate by showing unfolding twice and increasing more than 6 times at 100 ft / min speed.

Table II further compares the novel features in terms of tensile strength and elongation after exposure to 0, 5, 10, 15, and 20 megarads, at the start, and after one week of aging at 310 ° F.

Table II Dose (Megarad) 0 5 10 15 20 Pull (lb / inch) Starting 24 25 24 21 22 One week after 310 ° F 14 ^* 10 21 17 19 Elongation (%) Starting 12 13 13 12 13 310 One week after ゜ F 12 ^* 15 16 18 16 * The backing material melted, leaving only the cloth.

The above data illustrates that irradiation can maintain the structural integrity of the tape at elevated temperatures, but that the non-irradiated tape backing melted one week after aging at 310 ° F.

Table III illustrates comparative test results between the tape obtained in Example 1 and a commercially available polyvinyl chloride (PVC) tape which is the best high temperature resistant tape currently known to applicants. .

Table III illustrates the retention of the present invention in terms of tensile and elongation properties at elevated temperatures and most importantly, flexural properties during aging at elevated temperatures. The bending property data obtained by the ASTM D1388 cantilever guideline indicates that this method cannot measure bending properties of non-irradiated polyvinyl chloride tape, i.e., this tape is too hard,
Indicates that it was not flexible enough to be measured under the conditions of the TM guidelines.

Table IV illustrates the novel features of the tape produced in Example 2.

Table V illustrates the retention of tensile strength, elongation and modulus at 135 ° C. over a three week aging period.

Table V Flexural rigidity after aging (Test method-ASTM D 1388 Cantilever) -64 (Re-approved 1975) Example 1 151 Example 2 87.5 Polyvinyl chloride tape 1104 Table VI When tape is applied to automotive wires Bending properties after one week at 275 ° F. PVC Example 2 Cracks occur when bent and fall from wire bundle Remain intact even when bent The data shown in Table V shows that after aging the components in Table III, It shows that the shape flexibility and the high temperature resistance characteristics were simultaneously established. In particular, polyvinyl chloride tape is ten times worse in bending properties, that is, shape flexibility. This lack of bending properties leads to cracking and brittleness at elevated temperatures, as shown in Table VI.

Since certain changes can be made without departing from the scope of the invention described herein, all matter contained in the foregoing description (including examples) is illustrative and not limiting. Don't catch it.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C09J 7/02

Claims (8)

(57) [Claims] 1. A formable adhesive tape comprising a cross-linkable chlorinated polymer backing having a cross-linkable pressure-sensitive adhesive layer on one side, said backing layer being cross-linked, thereby forming the backing. The material layer is characterized as being resistant to high temperatures, and is also characterized as being flexible at elevated temperatures, and the adhesive layer is also crosslinked, thereby substantially increasing its resistance to shear at elevated temperatures. ing,
The tape. 2. The flexible adhesive tape according to claim 1, wherein said chlorinated backing material is chlorinated polyethylene. 3. The adhesive tape according to claim 2, wherein the adhesive is a bottom unwinding adhesive. 4. The adhesive tape according to claim 3, wherein the crosslinking is carried out by irradiation means. 5. The adhesive tape according to claim 4, wherein the irradiation is an electron beam. 6. The adhesive tape according to claim 5, wherein the dose of the electron beam is 5 to 20 Mrad. 7. The flexible adhesive tape according to claim 6, wherein the dose of the electron beam irradiation is 10 megarads. 8. The flexible adhesive tape of claim 1, wherein the tape is greater than 105 ° C. temperature resistance through standard use of the tape.