Male piece of the velvet type fastener

Abstract

In the velvet type fastener, each male element of the male piece consists of a stem and a cap laterally expanded at the top thereof, and is composed of compositions of a first and a second polyamide polymers having different melting points. These polymers are formed in crystalline composition in the stem and in amorphous composition in the cap. The stem consists of a core portion formed with the first polymer of lower melting point, and a sheath portion formed with the second polymer having a higher melting point. The cap consists of a core and outer layer portions formed with the first polymer, and an intermediate portion of a second polymer sandwiched therebetween.

Description

SUMMARY OF THE INVENTION

The present invention relates to an improvement of the male piece of the velvet type fastener, particularly it relates to an improvement of the male element provided with a laterally expanded cap formed at a top end portion of a stem projected upright from a base fabric of the male piece.

It is well known that there are two different kinds of velvet type fasteners. One of them is the fastener disclosed in the U.S. Pat. No. 3,009,235, and the other is the fastener disclosed in the U.S. Pat. No. 3,607,995. In the former fastener, the male piece is provided with a plurality of hook elements for engaging loop elements of the female piece, while in the latter fastener, a male element provided with a cap formed at the top end portion of a stem is utilized instead of the hook element. We have found from experience that the latter type of male element has a superior engaging function with a loop of a female element when a shearing force is applied between the male piece and the female piece, compared to the former male or hook element. As to the material for making the male element of the latter fastener, polyolefin or polyamide monofilament yarn have been preferably utilized, because of their desirable properties of elasticity, heat durability and strength, etc. However, from our experiences in practical use, we have found that the strength of the connected portion between the cap and the stem of the male element is insufficient and, consequently, the cap is apt to be broken off from the stem after repeated utilization of the fastener.

The principal object of the present invention is to eliminate the above-mentioned drawback of the velvet type fastener of the latter type.

The characteristic feature and composition of the velvet type fastener is hereinafter described with reference to the accompanying drawings and claims.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of an embodiment of a male piece according to the present invention;

FIGS. 2A - 2D are enlarged side views of the male pieces according to manufacturing steps of the velvet type fastener of the latter type;

FIG. 3 is an enlarged longitudinal cross sectional view of a male element of a conventional fastener of the latter type for the purpose of comparison with the present invention;

FIG. 4 is an enlarged longitudinal cross sectional view of a male element shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

To find a technical background of the present invention, the process for manufacturing the male piece of the velvet type fastener of the latter type was firstly analyzed. Referring to FIGS. 1, 2A to 2D, as disclosed in the specification of U.S. Pat. No. 3,607,995, the male piece is produced by the following steps: (1) a double woven fabric, wherein two base fabrics 2 are interconnected by connecting threads 1 made of monofilament yarn is produced; (2) the base fabrics 2 are separated each other by cutting the connecting threads 1 so that each separated base fabric 2 is provided with a plurality of upright monofilament piece 1'; (3) the separated base fabric 2 is coated with a bonding resin so as to fix the upright monofilament piece 1' thereto, consequently material fabric is produced; (4) next, the material fabric is passed through a water bath so as to cool the material, and immediately afterwards the material is carried to a heat treatment process in which the tip of each upright monofilament piece is fused by applying heat energy rapidly while the remaining portion thereof is maintained in crystalline composition; (5) after this heat treatment the material is passed through cool water so as to solidify the fused portions of the material.

According to the above-mentioned heat treatment, a plurality of male elements, composed of a stem portion 4a and a fused tip portion 4b thereof, can be formed on the base fabric 2, so that the male piece is produced as shown in FIG. 3. In the abovementioned manufacturing method, a pile knitted fabric can be utilized instead of the pile woven fabric.

Based on our common technical knowledge, if the synthetic resin material in crystalline composition is fused, this fused portion 4b has an amorphous composition. Consequently, it may be understood that the fused portion of the upright monofilament yarn of the male piece has an amorphous composition. As the tip portion is fused, this portion has a mushroom type shape expanded laterally. This portion is hereinafter referred to as a cap 4b, and the remaining upright portion of the monofilament yarn is hereinafter referred to as a stem 4a. As already illustrated, the cap 4b has an amorphous composition while the stem 4a has a crystalline composition. It must be understood that, there is not any critical boundary line between these amorphous compositions and the crystalline compositions. However, in the connecting or boundary portion between the stem and the cap, the composition of polyamide polymer is distinctively changed from the crystalline condition to the amorphous condition. Therefore, this connecting portion is one of the weak points of the male element. To conform the above-mentioned weakness of the boundary portion between the cap 4b and stem 4a of the male element, the microscopic observation of this portion was carried out. It was found that a certain number of male elements are provided with cracks formed in the boundary portion thereof. It may be interpreted that these cracks 5 are created according to the difference of heat-shrinkage between the cap and the top portion of the stem, effect of rapid heating and effect of rapid cooling. Therefore, if a strong shearing force is applied between an engaged male piece and female piece the above-mentioned cracks are expanded and finally in a certan number of male elements, the caps 4b are separated from the stems 4a thereof.

Both theoretical and experimental research has been carried out to eliminate the above-mentioned weak point in the boundary portion of each male element. As a result of this research the following very unique solution has been established. That is, in the present invention, as a material for the pile yarn, a nylon monofilament yarn having a configuration of a core portion 6a and a sheath portion 6 covering the core portion is utilized (FIG. 4). It is important to realize that the core portion 6a is made of a nylon polymer having a lower melting point, while the sheath portion 6 is made of another nylon polymer having a higher melting point than that of core portion. Therefore, when the above-mentioned heat treatment is applied to the material and the tip of the stem is fused, the tip of the core portion 6a and the tip of the sheath portion 6 are fused as shown in FIG. 4. As the melting point of the nylon polymer of the core portion 6a is lower than that of the sheath portion 6, the configuration of the cap is composed of a fused core portion 6b and outer layer 6c and an intermediate fused portion 6d formed between the core portion 6b and the outer layer 6c. As a result of our microscopic observations it was confirmed that the core portion 6b and the outer layer 6c are formed with a fused nylon polymer of the core portion 6d of the stem, while the intermediate portion 6d is formed with a fused nylon polymer of the sheath portion 6. Even if certain cracks 8 are formed in the boundary portion, as the inner terminal of cracks 8 cannot expand further because of the outer layer 6c, the above-mentioned drawback of the conventional fastener of the latter type can be effectively prevented. The experimental test which is hereinafter explained, proves this characteristic feature.

As to the polyamide polymer utilized for manufacturing the nylon monofilament yarn to produce the male element according to the present invention, it is preferable to use polycapramide (nylon 6) prepared by the polycondensation of .epsilon.-caprolactam or 6-aminocaproic acid, or a mixture thereof, polyhexamethylene adipamide (nylon 66), and polymers polycapramide or polyhexamethylene adipamide for their main ingredients and having the substantially same characteristics as those of polycapramide or polyhexamethylene adipamide, which may comprise one or more other components copolymerized with the above polymer forming monomer. These polymers may optionally comprise inorganic or organic materials of, for example, delustering agents, pigments, dyes, weather-proofing agents (ultraviolet ray absorbing agents), antistatic agents, plasticizers and flame-retardant agents. In the nylon monofilament yarn, two of these polymers having different melting points are used and conjugately spun into sheat-core type yarn. In order to obtain a yarn desirable to the purpose of the present invention, it is desirable that the difference of the melting point between the polymers composing the sheath-core type yarn is more than 20.degree.C, preferably from 40.degree. to 60.degree.C. When the difference of the melting point is less than 20.degree.C, it is difficult to cover the subsequently fused portion with the firstly fused portion at the time of the heat treatment. On the other hand, when the difference of the melting point is more than 60.degree.C, the cap cannot be in most cases normally formed, due to the fact that the amount of the fused polymer in the firstly fused portion becomes too large for the amount of the fused polymer in the subsequently fused portion.

For the two component polymers of the nylon monofilament 6-nylon according to the present invention, homopolymers such as nylon 6 and nylon 66 may be used in combination with each other. However, it is desirable that a known copolymerized nylon is used, as one of the two-component polymers, together with the above-mentioned homopolymer, or that polymers bearing therebetween the melting point difference of from 20.degree. to 60.degree.C are selected from the various types of copolymerized polyamides and used as the two component polymers. In general, it is preferable to use low melting point polyamides of a two-component system such as nylon -nylon 66, nylon6-nylon 610, nylon 6-nylon 6T or nylon 66-nylon 610, and a three-component system such as nylon 610-nylon 6-nylon 66. These two-component polymers can form the desired cap formation sufficient for practical use, if the difference of the melting point therebetween is less than 60.degree.C.

For practical utilization of the velvet type fastener according to the present invention, a monofilament yarn having a thickness in a range of 70 denier - 1000 denier, preferably 200 denier - 800 denier is used. It is required to use the drawn monofilament yarn having crystalline composition. However, the thicker monofilament may be used according to the end use of the fastener if the weaving or knitting operation can be carried out. With regard to the cross-sectional shape of the monofilament yarn, it is preferable to use a yarn having a circular cross-section wherein the core portion and the sheath portion have a concentric longitudinal axis.

The occupying ratio (in weight) of the core portion and the sheath portion in the monofilament yarn may be chosen in a range between 80/20 - 50/50.

Example

A monofilament yarn of 300 denier was prepared by using in the sheath portion nylon 6 having a melting point of 215.degree.C and prepared by polymerization of .epsilon.-caprolactam, and in the core portion copolymerized polyamide having a melting point of 170.degree.C and consisting of 52 parts of nylon 6 and 48 parts of nylon 66. The melt spinning was carried out at 280.degree.C by means of an ejecting nozzle for conjugate spinning of sheath-core type yarn and the occupying ratio of the sheath portion and the core portion in the obtained yarn was in 25 : 75 by weight. Then, the yarn was drawn in a conventional manner.

The above-mentioned monofilament yarn was utilized as a material for pile. A pile fabric was produced under the following conditions.

______________________________________ (a) Structure of a base fabric 2/1 rib weave (b) Warp yarn nylon multifilament 100 d/24 f weft yarn nylon multifilament 100 d/24 f (c) density warp yarn 30/inch weft yarn 25/inch (d) pile yarn 300 d nylon monofilament density 15/inch (e) a pile was formed at each 8 picks in an arrangement of plain weave (f) height of pile 2 mm ______________________________________

The above-mentioned pile fabric was supplied to a heat treatment process. In this process, the tip of the upright stems of the monofilament yarn was exposed to a heater maintained at 350.degree.C for 1/10 sec by carrying the material at a speed of 3 m/min, so that the tip of each upright stem of the monofilament yarn was fused. Consequently, the male elements were formed.

For the sake of comparative testing, two conventional fasteners were produced by utilizing 6 nylon monofilament yarn and a polypropylene monofilament yarn, by applying a similar manner of processing, except for the heat treatment temperature. (350.degree.C for the 6 nylon filament, 320 for the polypropylene filament). These male elements had the construction shown in FIG. 3, respectively. Next, repeated tests of the number of engaging and disengaging operations until at least one cap is separated, were carried out. Further, the resistances against disengaging were measured by applying the following tests. That is, after firmly engaging the male piece with the female piece, an end of the male piece was pulled upward from the female piece, and the force which was required to separate this end of the male piece from the female piece was measured by a spring balance. This resistance is referred to as a separation resistance (g/cm) in the table. Shearing resistance was measured by applying the following measured method. After firmly engaging the male piece with the female piece, a free end of the male piece and a free end of the female piece were gripped by a pair of grippers of a tensile test apparatus. In this test, the width of the sample pieces were 2 cm, respectively, the distance between the two grippers was 10 cm, the length of engaging portion was 2 cm. The force which was required to separate the male piece from the female piece was measured by this tensile test apparatus. A shearing force of kg/cm.sup.2 was then calculated from the above-mentioned measured force. The above-mentioned tests were also carried out after the male piece and the female piece were engaged and disengaged 3000 times.

Material of the monofilament Poly- 6 Present yarn for a pile propylene Nylon Invention yarn (Example) Test ______________________________________ Number of repeated test until at least one cap 370 520 1230 is broken off Initial condition Peeling test g/cm 98.2 112.5 103.5 Shearing force 3.1 3.2 3.1 kg/cm.sup.2 After 300 times of engagement and dis- engagement Peeling test g/cm 72.1 86.5 99.3 Resistance kg/cm.sup.2 2.3 2.1 3.0 ______________________________________

As it is clearly shown in the above-mentioned table, the improved male piece according to the present invention has superior quality in comparison with the conventional male piece.

Claims

What is claimed is:

1. In a male piece of a velvet type fastener provided with a plurality of male elements projected upright from a base fabric, an improvement comprising, each male element made of a synthetic monofilament yarn composed of a core portion extended along an axis thereof and a sheath portion encircling said core portion, said core portion composed of a first polyamide polymer of a lower melting point while said sheath portion is composed of a second polyamide polymer of higher melting point in comparison with said first nylon polyamide resin, said male element being composed of a stem and a laterally expanded cap formed at a top end portion of said stem, said cap being composed of a core and an outer layer formed with said first polyamide polymer and an intermediate portion being formed with said second polyamide polymer, the temperature difference between said melting points of said first and second polyamide polymers being between 40.degree. and 60.degree.C.

2. In a male piece of a velvet type fastener provided with a plurality of male elements projected upright from a base fabric, an improvement comprising, each male element made of a synthetic monofilament yarn composed of a core portion extended along an axis thereof and a sheath portion encircling said core portion, said core portion composed of a first polyamide polymer of a lower melting point while said sheath portion is composed of a second polyamide polymer of higher melting point in comparison with said first nylon polyamide resin, said male element being composed of a stem and a laterally expanded cap formed at a top end portion of said stem, said cap being composed of a core and an outer layer formed with said first polyamide polymer and an intermediate portion being formed with said second polyamide polymer, the temperature difference between said melting points of said first and second polyamide polymers being between about 20 and 60.degree.C.