GB2071722A

GB2071722A - Bonding yarn for veneers

Info

Publication number: GB2071722A
Application number: GB8108306A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-03-17
Filing date: 1981-03-17
Publication date: 1981-09-23
Also published as: JPS5849367B2; GB2071722B; JPS56130303A; CA1173339A

Abstract

A bonding yarn for a veneer including a plurality of filament yarns each formed by gathering a number of mono-filaments of a size of 50 to 250 deniers and twisting them 10 to 30 times per meter, said filament yarns being aligned in a belt-like form and then impregnated or coated with an adhesive to form a single tape-like yarn. <IMAGE>

Description

SPECIFICATION Bonding yarn for veneers This invention relates to an improvement in bonding yarns for veneers to be used for transversely bonding a number of veneers that are cut in a predetermined size into a belt-like sheet.

Background of Invention Conventionally, in transversely bonding plural veneers cut in a predetermined -size into a sheet by means of bonding yarns, the bonding yarns must have such a strength as not to be broken when the belt-like veneer formed by transversely bonding the plural veneers is moved during the drying step or during the laminating-bonding step. Hence, it is necessary to use those yarns which have a considerably large thickness.

If ordinary, thin, twisted filaments are aligned into a tape form, there can be obtained a bonding yarn having a desired strength. In the case of veneers having a thickness of 1 mm or more, the bonding yarns compress the veneers and are pushed into sheet surfaces so that ridges do not occur on the other side of the veneers.

When the veneers thinner than 1 mm are transversely bonded by the abovementioned tape like bonding yarn, however, the ridges do occur on the surface on the other side of the veneers.

Accordingly, in order to try to solve the abovementioned problem, the inventors of the present invention selected a perfectly untwisted yarn of 1000 deniers consisting of 250 monofilaments of a polyester as a yarn that can be easily expanded by a pushing force at the time of transversely bonding the veneers and that has a required strength, and passed this yarn through a solution of a thermoplastic adhesive and allowed the yarn to impregnate the adhesive to form a bonding yarn applied with the adhesive as shown in Figure 1(a). When the veneers were transversely bonded using this yarn, the strength of the bonding yarn was of course sufficient, but when the resulting veneer was transported and waS bent at the joint portions between the veneers, the bonding yarn underwent inter-layer peeling whereby the bonding yarn and the veneers were often separated from one another at that portion.

When the portion at which the inter-layer peeling occurred was examined, the amount of the adhesive was found to be extremely small while a large amount of the adhesive was found to have flowed out on both sides of the bonding yarn.

When the thin veneers formed by transversely bonding the individual veneers by the abovementioned 1000-denier bonding yarn were laminated and bonded together, ridges occurred on the surface opposite the bonding yarn. Thus, the bonding yarn was found to be unsuitable for transversely bonding the thin veneers.

Summary of Invention The present invention is directed to provide a bonding yarn for the veneers which maintains the characteristic that it is likely to expand in the direction of its width, does not undergo inter-layer peeling due to bending or the like, does not develop ridges as a result of the pushing force of the bonding yarn in transversely bonding the thin veneers together, and yet has an excellent bonding power.

Drawing The accompanying drawings show an embodiment of the present invention and a control embodiment, wherein Figure 1 (a) is a sectional view of the bonding yarn of the control; Figure 1 (b) is a sectional view of the bonding yarn of the present invention; Figure 2(a) is a sectional view showing the state of bonding of the control; and Figure 2(b) is a sectional view showing the state of bonding of the present invention.

Preferred Embodiment Hereinafter, the present invention will be described in detail. The mono-filaments to be used in the present invention consist of a synthetic fiber such as polyester, nylon or the like, and the unit yarn is formed by putting 20 to 50 monofilaments together and twisting them 10 to 30 times per meter.

Three to ten aggregate yarns thus formed are pulled out from plural bobbins and while they are being aligned in a flat sheet-like form, they are passed through a solution of an adhesive. After an excess amount of the adhesive is removed by passing the aggregate yarns through a pair of upper and lower rollers, the adhesive is hardened and the plural, aligned yarns are shaped into a single tape-like form as shown in Figure 1 (b). The tape-like yarn is then wound up onto a bobbin.

Incidentally, the number of the unit filaments is reduced for the thin veneers and is increased for the thick veneers. For bonding the thin veneers, it is preferred to align 50 to 70-denier filaments in such a number as to provide a required strength.

When the bonding yarn formed as described above is used for transversely bonding the veneers cut in a predetermined size, the adhesive between the unit filaments is prevented from flowing out by them. Since the number of twist of each unit filament is small, the adhesive is allowed to fluidize easily. Moreover, even when the same pressure as a single thick yarn is applied under heating, the pressure for a unit area is small because the pressure-bearing area is great, thereby allowing the expansion of the monofilaments in the direction of grooves, as well as the penetration and stay of the adhesive into the mono-filaments.Accordingly, each unit filament of the bonding yarn expands in the direction of its width, becomes extremely thin and comes into contact with other filaments so that even when the transversely bonded veneer is transported, strong bonding can be attained without causing peeling at any portion, and the inter-layer peeling does not occur at the butting portions at the side edges of the individual veneer sheets.

When the thin individual veneers are transversely bonded to form a bonded veneer sheet by use of the abovementioned bonding yarn and the resulting bonded sheets are laminated and bonded together using the bonding yarn, the ridges due to the bonding yarn do not occur at all on the sheet surface.

Further, the inventors carried out the peel test for the following bonding yarns A and B. The bonding yarn A was a perfectly untwisted yarn of a size of 1000 deniers consisting of 250 monofilaments of polyester and impregnated with a thermoplastic adhesive. The bonding yarn B was composed of four unit yarns, each consisting of 48 mono-filaments of polyester, having a size of 250 deniers and twisted 26 times per meter. The four unit yarns were aligned in a belt-like form and were then passed through the same thermoplastic adhesive as used in the bonding yarn A, and the excessive adhesive was removed. The bonding yarn B was the bonding yarn in accordance with the present invention.These bonding yarns A and B were heat-pressed onto the same veneers with a gap between them, and the peel test was effected six times by pulling the yarns A and B in the perpendicular direction to the sheet surface after cooling.

The results are illustrated in the Table below.

A (g) B (g) 1 450 630 2 500 600 3 580 620 4 570 650 5 470 680 6 630 630 average 533 635 As can be seen clearly from the above table, there is a distinctive difference in the bonding power between the bonding yarns A and B irrespective of the fact that the number of monofilaments of the bonding yarn B is smaller than that of the bonding yarn A. Whereas the bonding power of the bonding yarn B is stable, that of the bonding yarn A exhibits a large variance. It is thus found that the bonding yarn A is likely to undergo peeling at the portions where the bonding power is small.

While the embodiment disclosed herein is preferred, it will be appreciated that other variations and modifications will be obvious to those skilled in the art, and they are intended to be encompassed by the following claims.

Claims

1. A bonding yarn for a veneer including a plurality of filament yarns each formed by gathering a number of mono-filaments of a size of 50 to 250 deniers and twisting them 10 to 30 times per meter, said filament yarns being aligned in a belt-like form and then impregnated or coated with an adhesive to form a single tape-like yarn.

2. A yarn according to claim 1 including 20 to 50 mono-filaments in each yarn.

3. A yarn according to claim 1 or 2 including 3 to 10 filament yarns.

4. A bonding yarn for a veneer substantially as hereinbefore described with reference to and as illustrated in Figures 1 (b) and 2(b) of the accompanying drawings.

5. Veneers bonded using yarn according to any preceding claim.