CA2155404A1

CA2155404A1 - Textile structures containing linear low density polyethylene binder fibers

Info

Publication number: CA2155404A1
Application number: CA002155404A
Authority: CA
Inventors: James D. Geiman; Rakesh K. Gupta; Randall E. Kozulla; Richard J. Legare; Robert G. Maclellan
Original assignee: Hercules LLC
Current assignee: Hercules LLC
Priority date: 1994-08-09
Filing date: 1995-08-03
Publication date: 1996-02-10
Also published as: US5824613A; US5712209A; CN1123854A; KR960007850A; JPH0860510A; US5698480A; EP0696654A1

Abstract

A fiber comprising at least about 80% by weight linear low density polyethylene and having a melting point less than 109°C is disclosed. Also disclosed are thermally consolidated fiber structures comprising (1) at least about 3% by weight, based on the total weight of the structure, of lower melting binder fibers comprising at least 80% by weight linear low density polyethylene, preferably having a melting point less than 109°C, and (2) not more than 97% by weight, based on the total weight of the structure, of nonmelting fibers, or fibers having a melting point higher than the linear low density polyethylene fibers. The fiber structures can be in the form of multi filament yarns, woven or nonwoven textile fabrics, carpets, or laminates.

Description

21554~4 This invention relate~s to polyethylene fibers and to textile structures comp ~il,r a higher mPlting fiber and a lower InPlting binder fiber.
Textile structures are produced from a variety of materials both natural and m~n~n~dP. Numerous processes are used in the production of these structure~s, for 5 exa_ple, spinning, weaving, l~ni~ting, tufting, carding, and nee-llepunching. The structures thus produced can be tlimPncionally unstable. Several te~hni~lues are used to stabilize these structures, for eY~mphP, latex tre~tm~n~ or l~min~tion. Some of the~se tre~tlnPnts re~uire solvents or che-nir~lc with an undesirable environmental i nr~^t. Another technique is the blending of nona&esive fibers with potPnti~lly10 adhesive binder fibers to form a yarn or other textile structure, then a~Livalihg the potent;~lly adhesive fibers to bond them to the other fibers. The use of binder fiberc in stabilizing nonwoven materials is described in U.S. Patent Nos. 2,277,049 and2,464,301. Twisted yarns made with binder fibers having a mPlting point of 110-170C are described in European Patent No. 324,773. Wrap staple yarns cont~ining15 low l..PlI;,~g binder wrap strands based on copolyamides and copolyesters with melting points less than 149C are described in U.S. Patent No. 4,66~,552. Binder fibersmade from a blend of branched low density polyethylene having a m~lting point ofabout 107C and cryst~llinP polypropylene are disclosed in U.S. Patent No.
4,634,739. The use of polyethylene fibers with melting points higher than 110C, and 20 polypropylene fibers in nPellled, nonwoven webs is described in U.S. Patent Nos.
5,077,874 and 5,199,141. Re( ~lse of the small differential in the mPIting points of the two fibers, this combination of fibers in the nonwoven structure re~luires precise control of the heat tre~tmen~ temperatures to prevent any adverse effect on the primary fibers of the structure, i.e., polypropylene fibers.
It would therefore be desirable to provide a significant differential between the 5 I.,ellil,g point of the primary fibers of a textile structure and the binder fibers, providing a more fo ~iril~g l rocess for thermal t~ ent in the production of e..~ionally stable textile structures. This differential can be achieved by providing binder fibers with a s~ff;~iPn~ly low mPlting t~ ature. However, prior to the instant invention, no one has been able to produce binder fibers comprising linear low 10 density polyethylene fibers having a .-.el';..g point less than 109C.
This invention is directed to fibers comprising at least about 80% by weight linear low density pol~tLylene (LLDPE) having a melting point of less than 109C.
These fibers can be used in ffber structures of various kinds, which optionally contain fibers other than these LLDPE fibers.
In a preferred embo~linlent~ LLDPE fibers can be used to prepare ~limPn~ionally stable, lhc~ ally consolidated fiber structures comprising (1) at least about 3% by weight, based on the total weight of the structure, of lower meltingfibers cQmp ._~g at least 80% by weight linear low density polyethylene, and (2) not greater than about 97% by weight, based on the total weight of the structure, of20 nonmelting fibers, or fibers having a ~c!~;ng point higher than the linear low density polyethylene fibers.
The fiber structures are consolidated by heating to melt the linear low density polyethylene binder fibers without mPlt;n~ the higher mPl~;ng fibers. The fiber structures of this invention can be in the form of yarns, woven or nonwoven fabrics, 21~3~

carpets, and l~min~t~s in which at least one layer comprises a fiber structure of this invention.
The thermally consolidated fiber structures have improved dimensional stability, abrasion resistance, and wear properties. The linear low density 5 polyethylene binder fibers can provide a soft, flexible cloth-like fabric with good drape.
The fibers comprising at least about 80% by weight linear low density polyethylene are copolymers of ethylene and up to 20% by weight of a 3-12 carbonalpha-olefin such as, for example, propylene, butene, octene, and hexene. Alpha-10 olefins having 4-8 carbon atoms are preferred. Mixtures of the alpha-olefin comonomers can also be used, e.g., butene/octene or hexene/octene. The copolymers preferably comprise at least 80% ethylene. Linear low density polyethylene (LLDPE) is "linear", but with the alkyl groups of alpha-olefin comonomer pendentfrom the polymer chain, rather than having short chains of polymerized ethylene 15 units pendent from the main polymer chain as is the case with low density polyethylene. The density of LLDPE is typically about 0.88 to 0.94 g/cc. The melting point of the LLDPE fibers can vary depending upon the ratio of the ethylene monomer and the comonomer, and on the polymer structure.
Suitable linear low density polyethylenes include, for example, INSITETM, 20 ENGAGETM, and ASPUN~9 polyethylenes available from Dow Chemical Company, Midland, MichigPn, U.S.A., which have melting points of about 90 to 130C. The preferred fibers have melting points < 109C. Fibers spun from linear low density polyethylenes having melting points C 109C have not previously been available.

~5~gQ~

The linear low density polyethylene fibers can be crimped or uncrimped continuous filaments; crimped or uncrimped cut fibers, i.e., staple fibers, withlengths of about 3 to 150 millimeters (mm), preferably about 5-150 mm, and most preferably about 25-50 mm, or discrete microfibers, i.e., melt-blown fibers. The5 linear low density polyethylene fibers preferably have a denier of about 1-30, more preferably about 2-15, and most preferably about 2-6. In this specification the term "fibers" is meant to include all of the types of fibers and filaments described above.
The fibers can contain up to about 20%`by weight of other materials such as, forexample, stabilizers, pigments, additives and polymers other than linear low density 10 polyethylene (e.g., polypropylene, polystyrene, copolymers of olefins such as propylene, ethylene and butylene, etc., polyesters and polyamides ).
The fibers can have a nominal amount, for example, up to about 2% by weight, of a surface finish, which can be either hydrophilic or hydrophobic. Suitable fmishes include, for example, phosphate ester antistatic finishes, ethoxylated fatty 15 acid esters, and polydimethyl siloxanes. Such finishes are described, for example in U.S.Patent No. 4,938,832 and published European patent applications 486158, 557024, and 516412, the disclosures of which are incorporated by reference.
Linear low density polyethylene (LLDPE) fibers comprising at least about 80%
by weight linear low density polyethylene having a melting point less than 109C can 20 be used in fiber structures of various kinds, which optionally contain fibers other than the specified linear low density polyethylene fibers.
The fiber structures of this invention include yarns, for example, continuous filament, staple, wrap, or novelty yarns; woven or knitted textile fabrics; tufted textile fabrics such as velvet; loop pile or cut pile carpets; nonwoven fabrics or 2~ 55~Q~

structures, for example, needlepunched or hydroentangled nonwovens; and l~min~tes comprising several layers of the textile structures of this invention, or l~min~tes comprising at least one layer of a textile structure of this invention and at least one layer of another textile structure.
S In a preferred embodiment, LLDPE fibers are used in a thermally consolidated fiber structure comprising (1) at least about 3% by weight, based on the total weight of the structure, of lower melting fibers comprising at least about 80% by weight linear low density polyethylene, and (2) not greater than about 97% by weight, based on the total weight of the structure, of nonmelting fibers or fibers having a melting point higher than the linear low density polyethylene fibers. Typically the structures contain less than 50% by weight LLDPE fibers. A preferred range of LLDPE fibers is about 5 to about 20 weight %.
The second, higher melting fibers in the thermally consolidated structures of this invention can be any fiber that melts at least 10C higher than the Linear low density polyethylene fibers, preferably at least 20C higher, and most preferably at least 30C higher. When linear low density polyethylene fibers having a melting point < 109C are used with polypropylene fibers, the difference between the melting points of the two fibers can be >50C. These fibers can be crimped or uncrimped continuous filaments; crimped or uncrimped cut fibers, or discrete microfibers. Such ~Ibers include, for example, polypropylene, polyamide, and polyester fibers.
Polypropylene fibers are preferred. Nonmelting fibers can also be used. Such fibers include, for example, cotton, wool, acrylic, and rayon fibers. These fibers are preferably used in a range of about 80% to about 95% by weight.

2~s~

After the linear low density binder fibers and the higher melting fibers are combined, the binder fibers are melted by heating to bond the higher melting fibers to each other. After cooling, the polyethylene solidifies and locks the higher melting fibers in place, producing a dimensionally stable structure.
S The linear low density polyethylene multifilament yarns and staple fibers with a melting point of about 107C used in the following examples were prepared using ENGAGETM resin (le-sign~te~l 58200.03 available from The Dow Chemical Company, Midland, Mirhig~n, U.S.A. (Dow). The linear low density polyethylene multifil~ment yarns and staple fibers with a melting point of about 128C in the examples wereprepared using ASPUN~M resin designated 6835 available from Dow. These resins were meU extruded using a multi-hole spinnerette at temperatures of about 200 to 230C (normally spinning is carried out at 170-250C) and the extruded fibers were taken up on packages. These fibers were further drawn about 2 to 4 times to obtain the final denier per filament. The staple fibers were crimped and cut.
lS The polyethylene 300 denier/52 fil~ment continuous filament yarns used in the following examples had less than 2% of the surface finish TRYLUBE 7640A, available from Henkel Corporation, Ambler, PA, U.S.A. The polyethylene staple fibers had less than 2% of the surface finish LUROL PP912, available from George A. Goulston Co., Monroe, NC, U.S.A.
In this sperifir~t;on, all percentages are by weight unless otherwise noted.

Fx~mpl~ 1 Polypropylene (PP) bulked continuous m~lltifil~ment yarns were co-mingled with linear low density polyethylene (LLDPE) continuous m--ltifil~ment yarns to 2~ 5~4~

produce polypropylene/polyethylene composite yarns as shown in Table 1. The composite yarns were then heat-treated at the temperatures indicated in Table 1 for five minutes. Physical characteristics of the heat-treated yarns are also shown in this table. Dimensionally stable yarns with good bonding between the polypropylene 5 filaments were obtained.
Table 1 PE/
P~ rLLDPEHeat Treatment Heat-Treated Sample r~ ".O~ Yarn RatioT; . dlurc C~ r~ Yarn No. Yarn ~PP) (LLDPE)(%l%) ( C) Characteristics A 1 End of 1 End of 62/38 120"C Soft, and good S00 denier/ 300 denier/ bonding between 144 filaments 52 filaments fibers.
M.P. ~ 162C M.P. ~ 107C
0 B 2 Ends of 1 End of 77/23 120C Soft, andgood 500 denier/ 300 denier/ bonding between 144 filaments 52 filaments fibers.
M.P. - 162C M.P. - 107C
C 1 Endof 1 Endof 62/38 135C Hard, and good 500 denier/ 300 denier/ bonding between 144 filaments S2 filaments fibers.
M.P. z 162C M.P. - 128C

21~540~

F,Y~mpl~ ~
Polyester (PET) buL~ed continuous multifilament yarns were twisted with linear low density polyethylene (LLDPE) continuous multifilament yarns to produce polyester/polyethylene composite yarns as shown in Table 2. These twisted yarns were 5 then heat-treated at the temperatures indicated in Table 2 for five minutes. Physical characteristics of the heat-treated yarns are also shown in this table. Dimensionally twist-stable yarns with good bonding between the polyester filaments were obtained.

Table 2 PET/ Heat Heat-Treated Pul~ ' ^LLDPETreatment Cc- rC te Sample Polyester YarnRatio Temperature Yarn 0 No. Yarn (PET) (LLDPE)(%/%) (C) Cha~a~te.~lics D 2 Ends of 1 End of73/27 135C Soft, and good 400 denier/ 300 denier/ bonding between 94 filaments 52 filament fibers.
M.P. ~ 260C M.P. z 128C
E 4 Ends of 1 End of84/16 135C Soft, and good 400 denier/ 300 denier/ bonding between 94 filaments 52 filaments fibers.
M.P. ~ 260C M.P. z 128C
F 1 End of 1 End of57/43 135C Soft, and good 400 denier/ 300 denier/ bonding between 94 filaments 52 filaments fibers.
M.P. ~ 260C M.P. ~ 128C

21~4~

F,Y~mp~
Woven fabrics were prepared using different warp and filling yarns as shown in Table 3. LLDPE is linear low density polyethylene. These woven fabrics were then heat-treated at the temperatures indicated in Table 3 for 5 minutes. Physical 5 characteristics of the heat-treated fabrics are also indicated in this table.
Dimensionally stable fabrics with good bonding between fibers were obtained. In the table, den. = denier; fil. = filaments.

T ble3 M.P.
of Heat Heat-Treated Sample LLDPELLDPETreatment Fabric No. Warp Yarn Filling Yarn (%) (%) Temp. (C) Cha~ s G r~ d~" Alternate Ends 128 21 135 Soft, and good 500 denier of 300 den./52 bonding between staple spun yarn filaments LLDPE; fibers.
M.P. - 260C 400 den./92 fil.
pol~ester H P~ ~le., Alternate Ends 107 21 120 Soft, andgood 500 denier of 300 den./52 bonding between staplespun ~arn filaments LLDPE; fibers.
M.P. ~ 260C 400 den./92 fil.
pol~ester ~t~, Alternate Ends 107 21 120 Soft, and good 500 denier of 300 den./52 bonding between staplespun yarn filaments LLDPE; fibers.
M.P. - 260C 500 den./144 fil.
M.P. - 162C

Flr~mrlP 4 A nonwoven web with a basis weight of 62 g/yd2 was prepared using a 50%/50%
by weight blend of linear low density polyethylene 3 denier/filament staple fibers with a melting point of about 107C and polypropylene 2.2 denier/filament staple fibers with a melting point of about 162C. This nonwoven web was needlepunched to a 95 g/yd2 woven polyester fabric with a melting point of about 260C. Two samples of this fabric structure were each heat-treated for five minutes at 118C and then at 123C. The~se heat-treated fabric structures exhibited good dimensional stability and soft hand.
F.~mrl~ ~i A nonwoven web having a basis weight of 53 g/yd2 was prepared using a 2S%/7S% by weight blend of linear low density polyethylene 3 denier/filament staple fibers with a melting point of about 107C and polypropylene 2.2 denier/filament staple fibers with a melting point of about 162C. ~ ~min~tPs comprising two, four, and six layers of this nonwoven web were prepared and were each heat-treated at 120C for S
lS minutes. These heat-treated nonwoven structures exhibited good dimensional stability and soft hand.

21 5~404 F~mpl~ h A nonwoven web having a basis weight of 62 g/yd2 was prepared using a 50%/50% by weight blend of linear low density polyethylene 3 denier/filament staple fibers with a melting point of about 107C, and polypropylene 2.2 denier/filament S staple fibers with a melting point of about 162C. This nonwoven web was combined with a plain weave woven polyester fabric having a basis weight of 9S g/yd2, and the two structures were needlepunched together. This composite textile structure was then heat-treated at 120C for S minutes to substantiaUy melt the linear low density polyethylene fibers. The re~lt~nt textile structure exhibited good dimensional stability 10 and soft hand.
F,~mpl~ 7 A nonwoven web having a basis weight of 27 g/yd2 was prepared using linear low density polyethylene 5 denier/fil:~ment staple fibers with a melting point of about 107C. This nonwoven web was combined with a plain weave woven polyester fabric 15 having a basis weight of 95 g/yd2, and the two structures were needlepunched together.
This composite textile structure was then heat-treated at 120C for S minutes to sub~nti~lly melt the linear low density polyethylene fibers. The resultant textile structure exhibited g~od dimensional stability and soft hand.

~1~54Q4 F,Y~mple X
A nonwoven web having a basis weight of 48 g/yd2 was prepared using linear low density polyethylene 5 denier/filament staple fibers with a melting point of about 107C. This nonwoven web was combined with a plain weave woven polyester fabric 5 having a basis weight of 95 g/yd2, and the two structures were needlepunched together.
This composite textile structure was then heat-treated at 120C for S minutes to substantially melt the linear low density polyethylene fibers. The resultant textile structure exhibited good dimensional stability and soft hand.
Use of LLDPE provides fibers that are well suited for m~king fiber structures, 10 particularly with higher melting fibers of another polymer such as polypropylene, polyamide or polyester, or natural fibers. The fibers comprising LLDPE having a melting point less than 109C of this invention provide softer structures than those made with higher melting LLDPE. In addition, they enable the practioner to make structures at lower temperatures thereby red~lcing possible damage to the primary 15 fibers.

Claims

1. A fiber comprising at least about 80% by weight linear low density polyethylene having a melting point less than 109°C.

2. A fiber structure comprising fibers as claimed in claim 1.

3. A fiber structure comprising (1) fibers as claimed in claim 1, and (2) fibers other than the linear low density polyethylene fibers (1).

4. The structure of claim 2 or 3 in the form of a multifilament yarn, woven textile fabric, knitted textile fabric, tufted textile fabric, nonwoven textile fabric, or carpet.

5. A laminate comprising at least one layer of the structure of claim 4, wherein the structure is a nonwoven fabric.

6. A thermally consolidated fiber structure comprising (1) at least about 3% by weight, based on the total weight of the structure, of lower melting fibers comprising at least about 80% by weight linear low density polyethylene, and (2) not greater than about 97% by weight, based on the total weight of the structure, of nonmelting fibers or fibers having a melting point higher than the linear low density polyethylene fibers.

7. A thermally consolidated structure as claimed in claim 6 wherein the linear low density polyethylene has a melting point less than 109°C.

8. The structure of claim 6 or 7, wherein the difference in melting points between fiber (1) and fiber (2) is at least 10°C.

9. The structure of claim 8, wherein the difference in melting points between fiber (1) and fiber (2) is at least 30°C.

10. The structure of claim 9, wherein the difference in melting points between fiber (1) and fiber (2) is at least 50°C.

11. The invention of any of the preceding claims wherein the linear low density polyethylene is a copolymer of ethylene and at least one 3 to 12 carbon alpha-olefin and has a density of about 0.88 to about 0.94 g/cc.

12. The invention of claim 11 wherein the alpha-olefin is selected from the group consisting of propylene, butene, octene, hexene, and mixtures thereof.

13. The invention of claims 11 or 12 wherein the copolymer comprises at least 80% ethylene.

14. The structure of claims 6-13 wherein fiber (2) is selected from the group consisting of propylene, rayon, cotton, acrylic and wool fibers.

15. The structure of claims 6-13 wherein fiber (2) is a polypropylene, polyester or polyamide fiber.

16. The invention of any of the preceding claims wherein the linear low density polyethylene fibers are 1-30 denier staple fibers having a length of 3-150 mm.