AU598854B2 - Shock-resistant member - Google Patents

Description

N ~1 I: i 'I 59 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION FOR OFFICE USE 885m Form Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: 1 Fl i P r Related Art: TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: TOYO BOSEKI KABUSHIKI KAISHA 2-8, Dojima Hama 2-chome, Kita-ku, OSAKA, JAPAN Ichiro Yoshida and Toshikiyo Tanaka GRIFFITH HASSEL FRAZER 71 YORK STREET SYDNEY NSW 2000

AUSTRALIA

Complete Specification for the invention entitled: SHOCK-RESISTANT MEMBER The following statement is a full description of this invention, including the best method of performing it known to me/us:- 2024A:rk L .T.^J -L1 L -il 'i A~ltCA!ON ACCEPTED AND AMENDMENTS A LL W ED i

SPECIFICATION

The present invention relates to a shock-resistant, particularly ballistic-resistant member superior in energy absorbing property and particularly to a shock-resistant member comprising a nunber of layers of a high density woven fabric made of a high strength high modulus polyolefin multifilament yarn having a specified total denier value, said shock-resistant member being utilizable as bulletproof jackets, helmets, protective members of helicopters and 0° the like.

S° Prior Art 0 0 As for members adapted to absorb energy due to bullets and the like and used for bulletproof jackets, helmets and the like,' wholly aromatic polyamide filaments 0 0 have been commonly used as being preferable. The reasons are that wholly aromatic polyamide filaments are less 0" o heavy thin metal filaments and that even if a less amount of filament is used than conventional Nylon 6 or Nylon 66, a superior shock-absorbing effect can be exhibited; thus, they have an advantage that they contribute to easy handling and weight reduction (for example, if a person wears a bulletproof jacket made therefrom, he would be allowed to move nimbly.) However, since wholly aromatic polyamide filaments are expensive, it has been pointed 1Ax h Tatsuo' Nakahara Position: xecu.t.ive. V.ice. GRIFFITH HASSEL rRAZER G.P.O. BOX 4164 SYDNEY, AUSTRALIA .1

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*i i' 1 I* 09 D 0 0 o o 0 0 o of 1 o o 00 o* 0 r out that they have a drawback that they cannot be put in general use.

To overcome such drawback, a different synthetic filament has been developed, and techniques for using it have been proposed, such as those disclosed in EP 89537.

The techniques disclosed in the said EP specification make use of the properties of polyolefins having ultra high molecular weight with a weight average molecular weight of as much as 500,000 or more (which properties means that strength and elasticity are excellent), in producing an impact energy absorbing material which replaces wholly o, aromatic polyamide filaments, said techniques being S expected to be effective to some extent. Thus, it is S believed that ultra high molecular weight, high strength high modulus polyolefin filaments, which have higher shock resistance despite their relatively low melting points, can be put into practical use to form shock absorbing members for bulletproof jackets and the like.

When it is desired to obtain satisfactory shock resistance by the techniques described in the said EP patent specification, however, it is necessary to considerably increase the number of layers of a net-like fabric to be laminated, resulting in an increase in the weight of a bulletproof jacket or the like, a problem which makes it difficult for the wearer to move nimbly and detracts from wearing and handling qualities.

7794S/EI$ "-Vil ~y 2 i .I iI L-iil.i I ii-i According to the present invention, there is provided a shock-resistant member characterized in that a plurality of woven fabrics are laminated to serve as an impact energy absorbing material, the woven fabrics being densely woven of a high strength high modulus polyolefin multifilament yarn whose total denier is 100 600 d so that the sum of the warp and weft densities is 80 or more yarns/inch and so thatD x E is 2300 or less.

Embodiments of the invention may be lightweight and yet efficiently absorb shocks due to bullets and the like, 0 effectively exhibiting the function of protecting human oo bodies and the like.

o o OPERATION 00 0 o As described in EP 89537 mentioned above, in the case where ultra high molecular weight polyolefin fibers are used as an impact energy absorbing material, the intention is to 3 7794S/EM L\ -7

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obtain shock resistance by specifying the tensile strength and tensile modulus of the filaments. It is true that it cannot be denied that the physical properties of the filaments greatly influence the shock resistance, but our comparative investigations of the shock resistance of woven fabrics we actually made using polyolefin filaments of various ultra high molecular weights have revealed that the shock resistance is not less influenced by weave density per unit area than by the physical properties of 0000 the filaments from which the woven fabrics were made; it 09 00 has been ascertained that even if materials of the same 0080 m physical properties are used, depending on weave density there is produced a remarkable difference in shock resistance. Further, although it is necessary to increase the number of layers of a woven fabric to be laminated in order to improve shock resistance, laminating too many layers increases weight and bulk, leading to a problem 0 1 I about wearing quality. Thus, to provide a condition which allows lamination of as many layers as possible, it would £00 be contemplated to make the woven fabric lightweight and thin. To this end, however, weaving yarns must be made thin and lightweight, a fact which arouses a fear that this measure cannot always be thought to be effective for a shock-resistant material. On the other hand, the thinning of weaving yarns is expected to make it possible -4to increase weave density. With this in mind and thinking that in using high strength high modulus polyolefin multifilaments of ultra high molecular weight as raw materials, it is necessary to find the region where optimum yarn thickness and weave density which can contribute to increasing shock resistance lie, we have made various researches, which enabled us to hit on the arrangement of the present invention as described above.

More particularly, the invention makes it a prerequisite to use a multifilament made from a high o modulus polyolefin having an ultra high molecular weight.

a P tThe reason is that however great the influence of weave density is, satisfactory shock resistance cannot be A obtained if the strength and elasticity of the filament are poor.

o, The standards of high strength and high elasticity o° may be understood in terms of the general standards BO"o currently accepted; to give concrete values, the tensile strength is 20 or more g/denier and preferably 30 or more O4* g/denier, while the tensile modulus is 500 or more a*0* g/denier and preferably 800 or more g/denier, such physical properties being obtained by using an ultra high molecular weight polyolefin whose weight average molecular weight is 5 x 105 or more. In addition, the most preferable of the polyolefins are polyethylene and 5 -ii polypropylene; the use of polyethylene ensures the highest level of shock resistance.

In using such high strength high modulus polyolefin (hereinafter sometimes referred to simply as polyolefin), it is common practice to use it in the form of a multifilament consisting of a number of monofilaments, rather than in the form of a monofilament. Such multifilament, whether twisted, textured, doubled or otherwise, may have s small amount of other synthetic or natural filament blended therewith.

Another problem is whether to weave or to knit such polyolefin multifilament; we have decided on weaving, a° considering that knitting involves sparse use of yarn and results in poor shock absorbing capability at intersections. The weave construction is not specified at all, and plain weave, twill weave and satin weave may be freely employed. The conditions for obtaining satisfactory shock resistance, as described above, are that a polyolefin multifilament whose total denier is 100-600 d is used and that it is densely woven so that the sum of the warp and weft densities is or more yarns/inch and so that (3)JE x E is 2300 or less.

The reasons for these numerical restrictions will now be described.

In the case where the total denier was less than -6m I I i-i- I: 100 there was some expectation that the weave density could be sufficiently increased to enhance the effect of distributing impact energies coming from individual intersections, but actually the strength at intersections was so low as to cause rupture in the distributive transfer path of energy, correspondingly decreasing the impact energy absorbing effect and making the woven fabric extremely thin and easy to break; thus it was not practical. On the other hand, in the case where the total d denier exceeds 600 it becomes impossible to increase the weave density to the aforesaid specified value, so that the effect of distributing impact energies coming from individual intersections is decreased and hence the resulting shock resistance is insufficient. A more preferable value of total denier is in the range of 200-400 The thickness of the monofilaments constituting said multifilament is not particularly restricted, but if they are too thin they can easily break during spinning, offering a problem of productivity, and undesirably Sdecrease the impact energy distributing effect. On the other hand, if they are too thick the multifilament become rigid, making weaving operation difficult, and even if it is successfully woven, a garment made of the woven fabric obtained will feel unpleasant when worn; -7- 7 -XI- L L.IXIII^C~-(I~-IL iiiliU^.I l^_lili;~ii.Li ilii_~~ iill .I thus, it is recommended that the monofilament denier (d) d dn rfrhy is in the range of 1 20 and preferably 1.5-15 If the sum of the warp and weft densities is less than 80 yarns/inch, the number of intersections which distributively transfer impact energy is decreased, with the result that the amount of impact energy absorbed per unit area of the woven fabric is decreased, making it impossible to obtain satisfactory shock resistance.

However, if the multifilament is densely woven so that said sum is 80 or more yarns/inch, preferably 85 or more yarns/inch, or more preferably 90 or more yarns/inch, then the amount of impact energy distribution 0000 0 can be fully increased, making it possible to obtain superior shock resistance. However, if the value of D x E exceeds 2300, the weave density approaches the weave limit, so that even if the multifilament is successfully woven, a garment made of the woven fabric obtained will feel unpleasant when worn, and a garment made by laminating a required number of layers of the woven fabric wili considerably limit the freedom of the wearer's movement. However, if the weave conditions are controlled so thatj x E is 23 or less, preferably 2100 or less, or more preferably 2000 or less, the resulting woven fabric is soft without causing the troubles described above, and the freedom of wearer's movement -8-

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will not be lost even if a number of layers of the woven fabric are laminated.

The reason why the sum of the warp and weft densities and the value of jFDx E greatly influence the amount of impact energy absorption has been described above to some extent, and will now be described in more detail with reference to the accompanying drawing. In addition, Fig. 1 is a schematic view for explaining the reason why shock is alleviated by a shock-resistant member according to the invention.

00.q Fig. 1 schematically shows how an impact force 00 exerted by a bullet or the like hitting a woven fabric at a point is transferred. Suppose that an impact force 4o Q directed normal to the paper of the drawing acts at a point A. The impact energy is transferred to yarns; it is transferred around the point A through warp yarns 1 and weft yarns 2. This energy is attenuated as it is distributed in four directions at each intersection P between warp and weft yarns 1 and 2; thus, it is believed that the greater the number of intersections a woven fabric has, the quicker the transfer and attenuation of an impact force. That is, when a first woven fabric sparsely woven of thick filaments is compared with a second woven fabric densely woven of thin filaments, since the number of intersections P which accelerate the -9transfer and attenuation of impact energy is much greater in the first woven fabric than in the second, the first woven fabric is believed to be more effective in quickly distributing and lessening impact energy.

The force which prevents penetration of a bullet or the like is believed to be greater in thick-denier woven fabrics than in thin-denier woven fabrics, but when a comparison is made on the basis of woven fabrics having the same weight, the thin-denier woven fabric makes it possible to increase the number of layers to be laminated 6990 o and hence the number of intersections between. warp and sy weft yarns further increases, so that the amount of 4" impact energy absorption per unit area can be further *4t increased in the case of the thin-denier woven fabric, bringing about a favorable influence on improving the L0 shock resistance.

(i As is clear from the above description, a shock-resistant member is made by laminating a plurality of layers of a thin-denier densely woven fabric which satisfies the above-mentioned conditions. However, in some cases, other textile woven fabric or non-woven fabric or a film, polyester resin or epoxy resin, may be interposed between layers of the laminated woven fabric structure so as to add moistmre resistance, warmth retention and water resistance to the laminated 10 structure.

Of the shock-resistant members according to the invention, one using a high strength high modulus polyolefin filament will now be described briefly as to how it is produced.

i High strength high modulus polyolefin filaments are produced by dissolving "high molecular weight polyethylene having flexible high molecular chains" (for example, ultra high molecular weight polyethylene having a weight average !0 molecular weight of 1 x 105 or more, preferably 1 x 6 or more) in such a solvent as decalin, xylene or paraffin while heating (to temperatures below the boiling point of the solvent), feeding the polyethylene solution to a spinning device and extruding it into a hollow tube equipped with a cooling device at a temperature which prevents the polyethylene solution from solidifying. The filaments obtained contain the solvent therein, the solvent being then extracted, and the filaments are heated, without being dried, to a degree not melting them, and stretching them in one or more steps with a total stretch ratio of 10 or more: 1, preferably 20 or more: 1, so as to provide polyethylene filaments of about i 11 'd 71 7794S/EM 1-20 deniers. The polyethylene filaments are then made into multifilaments of 100-600 deniers in the usual manner, and the multifilaments are woven under controlled weave conditions so that the sum of the warp and weft weave densities is 80 or more yarns/inch and so that the value of ,f x E is 2300 or less. A plurality of layers of this woven fabric are laminated to provide a shock-resistant member of the present invention. In this laminating process, other woven fabric or non-woven fabric or a synthetic resin film or the like or polyester 0 resin, epoxy resin or the like may be interposed to A 4 improve the moisture resistance and other properties of a the laminated structure, as described above.

4 IExample The features of the invention will now be made more Sclear by giving an example of the invention.

Ultra high molecular weight polyethylene whose weight fill, average molecular weight was 1 x 10 6-1.8 x 106 and which had flexible high molecular chains was dissolved in decalin to prepare a spinning solution, the latter being &Ott then extruded into the atmosphere at a room temperature through a spinneret and cooled to provide gel fibers. The decalin was extracted from the gel fibers, whereupon the gel fibers were stretched at a temperature not melting them and with various stretch ratios to provide 12 monofilaments oi 0.8-22 deniers. The monofilaments were used to form multifilaments having total deniers D of 90-1120 and having characteristics listed in Table 1. The respective multifilaments were woven in plain or twill weave so that the resulting woven fabrics had respective total densities (E),JD x E values and weights listed in Table 1.

Also listed in Table 1 are the weight and other characteristics of a plain weave fabric made of a commercially available wholly aromatic polyamide filament (Kelver 49, product of Dupont) for comparison.

I Four layers of each woven fabric were thinly coated Swith epoxy resin over their surfaces and were laminated and pressed at 110 0 C for 3 hours, the resulting structure being used as a sample for evaluating bulletproofness.

Bulletproofness was evaluated by firing a 1.2-gram bullet from a 22-caliber revolver perpendicularly at each sample spaced 3 meters apart from the revolver and calculating the amount of energy absorbed by each sample from the difference between the velocities of the bullet before and after the sample. In addition, the tests were made twice for each sample, and the average was used for comparison. The velocity of the bullet was measured using a lumiline screen, the initial velocity being found to be 334 m/sec.

13 The results are collectively shown in table 1.

In Table 1, the tensile strength and tensile modulus of the multifilaments were tested by JIS-L1013 (1981), the bulletproofness being indicated in terms of absorption value per unit weight of the woven fabric, (J/Kg/m 2 The reason why "woven fabric weight relative to 7.84 J" was found is as follows.

e Since the absorption energy generally required for D 0 S.o bulletproof jackets is regarded as being "8 or more 0 kg-m," this value is divided by 1 J 0.102 kg-m to o r o determine the above-mentioned value.

14 0 0 oeg OQ 00 0 0 Sou o oo o o o 00 00 0 004 0 0t 0 4 0 a Ta l- 0 Table 1 Experiment No.

1 (this invention) 2 (this invention) 3 (this 4 invention) (Coum. ex.) 5 6 (Camp. ex.) (Caomp. ex.) 7 (Comp. ex.) No. invention) Kind of fiber Monofilament denier (d) Total denier (D) Tensile strength (g/D) Tensile nodulus (g/D) Weave density (warp) Yarns/inch (weft)

E

(warp weft) Woven fabric weight (g/m 2 VDTx E Weave structure Evaluation of woven fabric Bulletproofness (absorption energ J/kg/m

Z

Woven fabric weight relative to 7.84J (kg/m 2 Polyethylene 1.5 300 30 1100 50 50 100 145 1732 Plain Good 22.5 3.0 Polyethylene 2 300 30 1100 52 48 100 148 1732 2/1 twill Good 20.0 3.3 Polyethylene Polyethylene Polyethylene Polyethylene Wholly aronatic poly- Polyethylene Polyethylene ^amide (Kevler 29) 5 600 31 1080 40 40 80 226 1959 Plain Good 21.5 3.2 10 1120 31 1075 32 32 64 354 2141 Plain Good 17.5 3.7 1.0 90 33 1200 110 100 210 90 1992 Plain Easily breakable 30.0 2.7 20 700 31 1060 38 38 76 240 2010 Plain Good 18.0 4.2 1000 22 960 300 1897 Plain Good 17.4 From Table 1, the following can be said.

No. 7 uses the wholly aromatic polyamide which is considered to be the best at present. Although the result is good on the average, the cost is very high and the bulletproofness cannot be said to be good when compared with that of the present inventive articles.

Nos. 4 and 6 are examples in which the total denier of multifilaments exceeds 60 0 d. Since the sum of the warp and weft densities of the woven fabrics is less than 80 yarns/inch, the bulletproofness cannot be S0 said to be sufficient.

o In No. 5, the total denier D of the multifilament 0"o is less than 100 d Dense weave is possible and a high level of bulletproofness is obtained; however, since the multifilament is too thin, frequent yarn breaks occur, and since the woven fabric itself is easy to break, handling of the woven fabric is difficult.

Nos. 1-3 are examples which satisfy all the specified requirements of the invention. Their bulletproofness is higher than that of the one using wholly aromatic polyamide (No. and moreover the weaving and laminating operations are easy to perform.

The external appearance of these woven fabrics is good.

Further, it is seen that the weight of each woven fabric necessary to secure the unit absorption energy is much 16 less than the conventional value.

Advantages Brought about by the Invention The present invention arranged in the manner described above, using a woven fabric made with a particular weave density using a high strength high modulus polyolefin multifilament having a specified denier value, provides a shock-resistant member which is superior in handling and wearing qualities and capable of absorbing a large amount of impact energy. Therefore, S, this shock-resistant member can be widely used as a shock absorbing material for human body protection, such as

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i bulletproof jackets and helmets for military and guard purposes or protective garments for people who work at construction sites or ride motorcycles.

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Claims (14)

1. A shock-resistant member characterized in that a plurality of woven fabrics are laminated to serve as an impact energy absorbing material, the woven fabrics being densely woven of a high strength high modulus polyolefin multifilament yarn whose total denier is 100-600 so that the sum of the warp and weft densities is 80 or more yarns/inch and so thatD x E is 2300 or less.

2. A shock-resistant member as set forth in Claim 1, wherein the tensile strength of the high strength high O modulus polyolefin multifilament yarn is 20 or more S g/denier. ou

3. A shock-resistant member as set forth in Claim 1, wherein the tensile strength of the high strength high modulus polyolefin multifilament yarn is 30 or more g/denier.

4. A shock-resistant member as set forth in Claim 1, wherein the initial tensile modulus of the high strength high modulus polyolefin multifilament yarn is 500 Is 20 or more g/denier.

A shock-resistant member as set forth in Claim +rs' 1, wherein the initial tensile modulus of the high strength high modulus polyolefin multifilament yarn is 800 or more g/denier. 7794/18 7794S/EM -6- UI. ~--se I _II.

6. wherein

7. wherein

8. wherein

9. wherein modulus wherein A shock-resistant member as set forth in Claim 1, the woven fabric is of plain weave. A shock-resistant member as set forth in Claim 1, the woven fabric is of twill weave. A shock-resistant member as set forth in Claim 1, the polyolefin is polyethylene or polypropylene.

A shock-resistant member as set forth in Claim 1, the total denier of the high strength high polyolefin multifilament yarn is 200-400 d A shock-resistant member as set forth in Claim 1, the fineness of the monofilaments constituting 6060 6000 01 1 0t 46 on 0 n no 0010 0 6 0 the multifilament is 1-20 deniers.

11. A shock-resistant member as wherein the sum of the warp and or more .arns/inch.

12. A shock-resistant member as wherein the sum of the warp and or more yarns/inch.

13. A shock-resistant member as whereinD x E is 2100 or less.

14. A shock-resistant member as whereinjD x E is 2000 or less. set forth in Claim 1, weft densities is set forth in Claim 1, weft densities is set forth in Claim 1, set forth in Claim 1, 19 .l~gC i A shock-resistant member substantially as hereinbefore described with reference to the drawing and any one of Examples 1 to 3. 0 o Dated this 4th day of September 1987 o 0 TOYO BOSEKI KABUSHIKI KAISHA X o By their Patent Attorney GRIFFITH HASSEL FRAZER