US20150284879A1 - Water-disintegrable composite fiber and method for producing the same - Google Patents

Water-disintegrable composite fiber and method for producing the same Download PDF

Info

Publication number
US20150284879A1
US20150284879A1 US14/421,560 US201314421560A US2015284879A1 US 20150284879 A1 US20150284879 A1 US 20150284879A1 US 201314421560 A US201314421560 A US 201314421560A US 2015284879 A1 US2015284879 A1 US 2015284879A1
Authority
US
United States
Prior art keywords
resin
water
fiber
pga
acid resin
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US14/421,560
Other languages
English (en)
Inventor
Takeo Takahashi
Yukitoshi Chiba
Masahiro Yamazaki
Hiroyuki Sato
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kureha Corp
Original Assignee
Kureha Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kureha Corp filed Critical Kureha Corp
Assigned to KUREHA CORPORATION reassignment KUREHA CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: TAKAHASHI, TAKEO, CHIBA, YUKITOSHI, SATO, HIROYUKI, YAMAZAKI, MASAHIRO
Publication of US20150284879A1 publication Critical patent/US20150284879A1/en
Abandoned legal-status Critical Current

Links

Images

Classifications

    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
    • D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
    • D01F8/14—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one polyester as constituent
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
    • C09K8/02—Well-drilling compositions
    • C09K8/03—Specific additives for general use in well-drilling compositions
    • C09K8/035—Organic additives
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/08—Melt spinning methods
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/26—Formation of staple fibres
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
    • D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
    • D01F6/62—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters
    • D01F6/625—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters derived from hydroxy-carboxylic acids, e.g. lactones
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K2208/00—Aspects relating to compositions of drilling or well treatment fluids
    • C09K2208/08—Fiber-containing well treatment fluids
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/08—Melt spinning methods
    • D01D5/084—Heating filaments, threads or the like, leaving the spinnerettes
    • D—TEXTILES; PAPER
    • D10—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
    • D10B—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
    • D10B2331/00—Fibres made from polymers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polycondensation products
    • D10B2331/04—Fibres made from polymers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polycondensation products polyesters, e.g. polyethylene terephthalate [PET]
    • D10B2331/041—Fibres made from polymers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polycondensation products polyesters, e.g. polyethylene terephthalate [PET] derived from hydroxy-carboxylic acids, e.g. lactones
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2913—Rod, strand, filament or fiber
    • Y10T428/2929—Bicomponent, conjugate, composite or collateral fibers or filaments [i.e., coextruded sheath-core or side-by-side type]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2913—Rod, strand, filament or fiber
    • Y10T428/2929—Bicomponent, conjugate, composite or collateral fibers or filaments [i.e., coextruded sheath-core or side-by-side type]
    • Y10T428/2931—Fibers or filaments nonconcentric [e.g., side-by-side or eccentric, etc.]

Definitions

  • the present invention relates to a water-disintegrable composite fiber and a method for producing the same, and particularly to a water-disintegrable composite fiber containing a polyglycolic acid resin and a polylactic acid resin and a method for producing the same.
  • fibers consisting of a polylactic acid resin or a polyglycolic acid resin are known as fibers having biodegradability or bioabsorbability and have been conventionally used as surgical sutures and the like in the medical field.
  • the applications of such fibers have been expanded not only to the medical field but also to a wide range of fields, such as fibers to be used in industrial materials, sanitary materials, and lifestyle materials.
  • single fibers of a polylactic acid resin or a polyglycolic acid resin cannot necessarily be considered to have sufficient water disintegrability or mechanical characteristics, and the conjugation of single fibers with various resins has been studied (for example, Japanese Unexamined Patent Application Publication No. H07-133511 (Patent Document 2), Japanese Unexamined Patent Application Publication No. 2000-265333 (Patent Document 3), and Japanese Unexamined Patent Application Publication No. 2007-119928 (Patent Document 4)).
  • Patent Document 1 Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2011-506791
  • Patent Document 2 Japanese Unexamined Patent Application Publication No. H07-133511A
  • Patent Document 3 Japanese Unexamined Patent Application Publication No. 2000-265333A
  • Patent Document 4 Japanese Unexamined Patent Application Publication No. 2007-119928A
  • Polylactic acid resin fibers exhibit good water disintegrability at relatively high temperatures of 80° C. or higher.
  • proppants in the well treatment fluid tend to settle, and it has been difficult to obtain a well treatment fluid with excellent proppant dispersibility.
  • the present invention was conceived in light of the problem of the conventional technology described above, and an objective of the present invention is to provide a water-disintegrable composite fiber capable of maintaining high proppant dispersibility in a well treatment fluid and a method for producing the fiber.
  • the present inventors discovered that the dispersibility of proppants is reduced in a well treatment fluid to which short fibers consisting of a polylactic acid resin have been added, because the diameter of the polylactic acid resin short fibers is large and the contact area between fibers and proppants is small.
  • the present inventors discovered that polylactic acid resin fibers cannot be drawn at a high draw ratio and that it is difficult to obtain polylactic resin fibers with a small diameter.
  • D-form ratio D-lactic acid units
  • the present inventors discovered that by including a prescribed amount of a polyglycolic acid resin with respect to the D-lactic acid units in a water-disintegrable composite undrawn yarn comprising a phase containing a polyglycolic acid resin and a phase containing a polylactic acid resin having D-lactic acid units, it is possible to draw the composite undrawn yarn at a high draw ratio and it is possible to obtain a water-disintegrable composite drawn yarn with a small diameter, and the present inventors thereby completed the present invention.
  • the water-disintegrable composite fiber of the present invention is an undrawn or a drawn fiber comprising a phase containing a polyglycolic acid resin and a phase containing a polylactic acid resin with a D-lactic acid unit ratio of at least 1.0%; the two phases being respectively continuous in the length direction; a region formed by the phase containing the polyglycolic acid resin having a cross section with an area ratio of at most 50%; and the content of the polyglycolic acid resin being from 2 to 100 parts by mass per 1 part by mass of the D-lactic acid units in the polylactic acid resin.
  • Such a water-disintegrable composite fiber preferably further has a side surface in which the region formed by the phase containing the polyglycolic acid resin has an area ratio of at most 50%.
  • the fiber structure is preferably at least one type selected from a core-sheath type, a multicore type, a side-by-side type, a multiple division type, a multilayer type, and a radial type structure.
  • the single fiber fineness of the drawn water-disintegrable composite fiber is preferably at most 3.0 denier.
  • fibers of various structures such as hollow fibers or ultrafine fibers can be obtained by removing either the polyglycolic acid resin or the polylactic acid resin from the water-disintegrable composite fiber of the present invention, and a water-disintegrable composite staple fiber can be obtained by cutting the water-disintegrable composite fiber of the present invention.
  • This water-disintegrable composite staple fiber can be suitably used as an additive at the time of oil or gas drilling.
  • the method for producing the water-disintegrable composite fiber of the present invention is a method comprising the steps of forming a fibrous composite by continuously discharging a polylactic acid resin having a D-lactic acid unit ratio of at least 1.0% and from 2 to 100 parts by mass of a polyglycolic acid resin per 1 part by mass of D-lactic acid units in the polylactic acid resin from a spinneret for composite fibers, each being discharged in a molten state and cooling the fibrous composite to obtain an undrawn yarn comprising a phase containing the polyglycolic acid resin and a phase containing the polylactic acid resin, the undrawn yarn having a cross section in which the region formed by the phase containing the polyglycolic acid resin has an area ratio of at most 50%.
  • the undrawn yarn may be drawn so as to obtain a drawn yarn comprising the phase containing the polyglycolic acid resin and the phase containing the polylactic acid resin, the drawn yarn having a cross section in which the region formed by the phase containing the polyglycolic acid resin has an area ratio of at most 50%, and the drawn yarn containing from 2 to 100 parts by mass of the polyglycolic acid resin per 1 part by mass of the D-lactic acid units in the polylactic acid resin.
  • the polyglycolic acid resin is easily subjected to the necking phenomenon due to drawing, so the low orientation of the polylactic acid resin is compensated by the high orientation of the polyglycolic acid resin. Therefore, the concentration of stress is unlikely to occur even when drawn at a high draw ratio, and it is speculated that this is why fiber is unlikely to break.
  • FIG. 1A is a schematic view illustrating a preferred embodiment of the structure of a concentric core-sheath type water-disintegrable composite fiber of the present invention.
  • FIG. 1B is a schematic view illustrating a preferred embodiment of the structure of an eccentric core-sheath type water-disintegrable composite fiber of the present invention.
  • FIG. 1C is a schematic view illustrating a preferred embodiment of the structure of a multicore type water-disintegrable composite fiber of the present invention.
  • FIG. 1D is a schematic view illustrating a preferred embodiment of the structure of a side-by-side type water-disintegrable composite fiber of the present invention.
  • FIG. 1E is a schematic view illustrating a preferred embodiment of the structure of a multiple-division type water-disintegrable composite fiber of the present invention.
  • FIG. 1F is a schematic view illustrating a preferred embodiment of the structure of a multilayer type water-disintegrable composite fiber of the present invention.
  • FIG. 1G is a schematic view illustrating a preferred embodiment of the structure of a radial type water-disintegrable composite fiber of the present invention.
  • FIG. 2 is a schematic view illustrating a melt spinning device used in the working examples and comparative examples.
  • FIG. 3 is a schematic view illustrating a drawing device used in the working examples and comparative examples.
  • the water-disintegrable composite fiber of the present invention comprises a phase containing a polyglycolic acid resin (abbreviated as a “PGA resin phase” hereafter) and a phase containing a polylactic acid resin with a D-lactic acid unit ratio (D-form ratio) of at least 1.0% (abbreviated as a “PLA resin phase” hereafter).
  • PGA resin phase a phase containing a polyglycolic acid resin
  • PDA resin phase a phase containing a polylactic acid resin with a D-lactic acid unit ratio (D-form ratio) of at least 1.0%
  • the polylactic acid resin (abbreviated as the “PLA resin” hereafter) used in the present invention contains D-lactic acid units in an amount of at least 1.0%.
  • D-lactic acid units in an amount of at least 1.0%.
  • Specific examples include poly-DL lactic acids with a D-form ratio of at least 1.0% (copolymers of D-lactic acid and L-lactic acid (including ring-opened polymers of D/L-lactides, which are bimolecular cyclic esters of D-lactic acid and L-lactic acid), abbreviated as “PDLLA resins” hereafter) and poly-D lactic acids (homopolymers of D-lactic acid (including ring-opened polymers of D-lactides, which are bimolecular cyclic esters of D-lactic acid), abbreviated as “PDLA resins” hereafter) and the like.
  • the D-form ratio of the PLA resin is less than 1.0%, the water disintegrability (mass loss) of the PLA resin phase decreases, and the water disintegrability (mass loss) of the composite fiber also decreases.
  • the D-form ratio of the PLA resin is preferably at least 1.2% from the perspective that the water disintegrability of the PLA resin phase increases.
  • the upper limit of the D-form ratio of the PLA resin is not particularly limited but is preferably at most 30% and more preferably at most 15% from the perspective of ensuring that the action due to the polyglycolic acid resin described below is sufficiently expressed.
  • the melt viscosity of the PLA resin (temperature: 240° C., shear rate: 122 sec) is preferably from 1 to 10,000 Pa ⁇ s, more preferably from 20 to 6,000 Pa ⁇ s, and particularly preferably from 50 to 4,000 Pa ⁇ s.
  • the melt viscosity is less than the lower limit described above, the spinnability is diminished and the fiber tends to have break in some parts, whereas when the melt viscosity exceeds the upper limit described above, it tends to become difficult to discharge the PLA resin in a molten state.
  • such a PLA resin may be used alone, and various additives such as thermal stabilizers, end-capping agents, plasticizers, and UV absorbers or other thermoplastic resins may be added as necessary and used as a PLA resin composition.
  • the polyglycolic acid resin (abbreviated as “PGA resin” hereafter) used in the present invention is a glycolic acid homopolymer consisting of repeating units of a glycolic acid represented by the following formula (1) (abbreviated as “PGA homopolymer” hereafter; including glycolide ring-opened polymers, which are bimolecular cyclic esters of glycolic acids):
  • Such a PGA resin can be synthesized by the dehydration polycondensation of a glycolic acid, de-alcohol polycondensation of a glycolic acid alkyl ester, the ring-opening polymerization of a glycolide, or the like.
  • the PGA homopolymer is preferably synthesized by the ring-opening polymerization of a glycolide.
  • such ring-opening polymerization can be performed by bulk polymerization or solution polymerization.
  • catalysts used when producing the PGA resin by the ring-opening polymerization of a glycolide include publicly known ring-opening polymerization catalysts such as tin compounds such as tin halide and organic tin carboxylate; titanium compounds such as alkoxy titanate; aluminum compounds such as alkoxyaluminum; zirconium compounds such as zirconium acetyl acetone; and antimony compounds such as antimony halide and antimony oxide.
  • tin compounds such as tin halide and organic tin carboxylate
  • titanium compounds such as alkoxy titanate
  • aluminum compounds such as alkoxyaluminum
  • zirconium compounds such as zirconium acetyl acetone
  • antimony compounds such as antimony halide and antimony oxide.
  • the PGA resin can be produced by a conventionally known polymerization method, but the polymerization temperature is preferably from 120 to 300° C., more preferably from 130 to 250° C., and particularly preferably from 140 to 220° C. When the polymerization temperature is less than the lower limit described above, polymerization tends to not progress sufficiently, whereas when the polymerization temperature exceeds the upper limit described above, the resin that is produced tends to be pyrolyzed.
  • the polymerization time of the PGA resin is preferably from 2 minutes to 50 hours, more preferably from 3 minutes to 30 hours, and particularly preferably from 5 minutes to 18 hours.
  • the polymerization time is less than the lower limit described above, polymerization tends to not progress sufficiently, whereas when the polymerization time exceeds the upper limit described above, the resin that is produced tends to be discolored.
  • the weight average molecular weight of such a PGA resin is preferably from 50,000 to 800,000, and more preferably from 80,000 to 500,000.
  • the weight average molecular weight of the PGA resin is less than the lower limit described above, the mechanical strength of the resulting composite fiber tends to be diminished, whereas when the weight average molecular weight exceeds the upper limit described above, it tends to become difficult to discharge the PGA resin in a molten state.
  • the weight average molecular weight is a value in terms of polymethyl methacrylate measured by gel permeation chromatography (GPC).
  • the melt viscosity of the PGA resin (temperature: 240° C., shear rate: 122 sec) is preferably from 1 to 10,000 Pa ⁇ s, more preferably from 50 to 6,000 Pa ⁇ s, and particularly preferably from 100 to 4,000 Pa ⁇ s.
  • the melt viscosity is less than the lower limit described above, the spinnability is diminished and the fiber tends to break in some parts, whereas when the melt viscosity exceeds the upper limit described above, it tends to become difficult to discharge the PGA resin in a molten state.
  • such a PGA resin may be used alone, and various additives such as thermal stabilizers, end-capping agents, plasticizers, and UV absorbers or other thermoplastic resins may be added as necessary and used as a PGA resin composition.
  • a polyglycolic acid copolymer comprising repeating units of a glycolic acid represented by the aforesaid formula (1) (abbreviated as a “PGA copolymer” hereafter) may also be used instead of such a polyglycolic acid resin.
  • the PGA copolymer described above can be synthesized by using a comonomer in a polycondensation reaction or ring-opening polymerization reaction for synthesizing a PGA homopolymer.
  • a comonomer include cyclic monomers such as ethylene oxalate (i.e. 1,4-dioxane-2,3-dione), lactides, lactones (e.g. ⁇ -propiolactone, ⁇ -butyrolactone, ⁇ -pivalolactone, ⁇ -butyrolactone, ⁇ -valerolactone, ⁇ -methyl- ⁇ -valerolactone, ⁇ -caprolactone, and the like), carbonates (e.g.
  • trimethylene carbonate and the like ethers (e.g. 1,3-dioxane and the like), ether esters (e.g. dioxanone and the like), and amides (e.g. ⁇ -caprolactam and the like); hydroxycarboxylic acids such as lactic acid, 3-hydroxypropanoic acid, 3-hydroxybutanoic acid, 4-hydroxybutanoic acid, 6-hydroxycaproic acid, and the alkylesters thereof; mixtures containing substantially equimolar amounts of aliphatic diols, such as ethylene glycol and 1,4-butanediol, and aliphatic dicarboxylic acids, such as succinic acid and adipic acid, or the alkyl esters thereof.
  • aliphatic diols such as ethylene glycol and 1,4-butanediol
  • succinic acid and adipic acid or the alkyl esters thereof.
  • One type of these comonomers may be used alone
  • the water-disintegrable composite fiber of the present invention is an undrawn or a drawn yarn comprising a phase containing a PGA resin (PGA resin phase) and a phase containing a PLA resin with a D-form ratio of at least 1.0% (PLA resin phase); the two phases being respectively continuous in the length direction of the fiber; the composite fiber having a cross sectional area partly formed by the PGA resin phase with an area ratio of at most 50%; and the fiber containing from 2 to 100 parts by mass of the PGA resin per 1 part by mass of the D-lactic acid units in the PLA resin.
  • PGA resin phase PGA resin phase
  • PLA resin phase PLA resin with a D-form ratio of at least 1.0%
  • the content of the PGA resin per 1 part by mass of the D-lactic acid units in the PLA resin is less than 2 parts by mass, the undrawn yarn cannot be drawn at a high draw ratio, which makes it difficult to form a drawn yarn with a small single fiber fineness and reduces the proppant dispersibility by the drawn composite fiber.
  • the PGA resin content exceeds 100 parts by mass, the proportion of the PLA resin is small, so the characteristics of the PLA resin cannot be sufficiently expressed.
  • a relatively high temperature specifically 60° C. or higher, the rate of water disintegration of the composite fiber becomes very high, and the use of the fiber becomes difficult.
  • the PGA resin content is preferably from 3 to 100 parts by mass and more preferably from 5 to 80 parts by mass per 1 part by mass of the D-lactic acid units in the PLA resin from the perspective of obtaining a drawn composite fiber with a small single fiber fineness when the undrawn yarn is drawn at a high draw ratio, excellent proppant dispersibility, and excellent water disintegrability at a relatively high temperature of 60° C. or higher.
  • the content of the PGA resin in the component constituting the PGA resin phase is preferably at least 60 mass %, more preferably at least 80 mass %, even more preferably at least 95 mass %, and particularly preferably 100%.
  • the content of the PLA resin in the component constituting the PLA resin phase is preferably at least 60 mass %, more preferably at least 80 mass %, even more preferably at least 95 mass %, and particularly preferably 100%.
  • the area formed from the PGA resin phase is 50% or less in terms of area ratio.
  • the area ratio of the region formed by the PGA resin phase in the cross section exceeds 50%, the proportion of the PLA resin is small, so the characteristics of the PLA resin cannot be sufficiently expressed, and the water disintegrability (mass loss) of the composite fiber at a relatively high temperature of 60° C. or higher decreases.
  • the area ratio of the region formed by the PGA resin phase in the cross section is preferably at most 40% from the perspective that the water disintegrability (mass loss) of the composite fiber at a relatively high temperature of 60° C. or higher improves.
  • the lower limit of the area ratio of the region formed by the PGA resin phase in the cross section of the water-disintegrable composite fiber of the present invention is preferably at least 1%, more preferably at least 5%, even more preferably at least 10%, and particularly preferably at least 15%.
  • the area ratio of the region formed by the PGA resin phase in the cross section is less than the lower limit described above, the characteristics of the PGA resin cannot be sufficiently expressed, so the undrawn yarn cannot be drawn at a high draw ratio, which makes it difficult to form a drawn yarn with a small single fiber fineness and tends to diminish the proppant dispersibility of the composite fiber (drawn yarn). Further, the water disintegrability (mass loss) of the composite fiber at around 60° C. tends to decrease.
  • the area ratio of the region formed by the PGA resin phase on the side surface of the water-disintegrable composite fiber of the present invention is preferably at most 50%, more preferably at most 30%, even more preferably at most 15%, and particularly preferably at most 10%.
  • the area ratio of the region formed by the PGA resin phase on the side surface exceeds the upper limit described above, the undrawn yarn is prone to agglutination, and the unwindability after storage, particularly at high temperature and high humidity (for example, at a temperature of 40° C. and relative humidity of 80% RH), tends to be diminished.
  • the region formed from the PGA resin phase not to be exposed to the side surface of the water-disintegrable composite fiber of the present invention, so the lower limit of the area ratio is particularly preferably 0% or higher.
  • fiber structures of the water-disintegrable composite fiber of the present invention include a concentric core-sheath type structure (see FIG. 1A ), an eccentric core-sheath type structure (see FIG. 1B ), a multicore type structure (see FIG. 1C ), a side-by-side type structure (see FIG. 1D ), a multiple-division type structure (see FIG. 1E ), a multilayer type structure (see FIG. 1F ), a radial type structure (see FIG. 1G ), and composite structures combining two or more types thereof.
  • FIGS. 1A to 1G the left figure is a schematic view of the cross section of the composite fiber, and the right figure is a schematic view of the side surface.
  • A represents the PGA resin phase
  • B represents the PLA resin phase.
  • a concentric core-sheath structure, an eccentric core-sheath structure, or a multicore structure is preferable from the perspective that the undrawn yarn has excellent unwindability, the fiber is unlikely to break when drawn and that the drawn yarn has a small single fiber fineness and excellent proppant dispersibility.
  • the mass loss of the drawn yarn when immersed for 14 days in water at 60° C. and 80° C. is preferably at least 10%, more preferably at least 15%, even more preferably at least 20%, yet even more preferably at least 25%, and particularly preferably at least 30%.
  • the mass loss is less than the lower limit described above, the fiber is not sufficiently hydrolyzed and may remain in the ground after well treatment when added to a well treatment fluid as a short fiber.
  • the upper limit of the mass loss described above is not particularly limited and is preferably 100% or less, but the upper limit may also be 95% or less.
  • the undrawn yarn can be drawn at a high draw ratio, this can be drawn to obtain a drawn yarn with a single fiber fineness of preferably at most 3.0 denier, more preferably at most 2.0 denier, and particularly preferably at most 1.5 denier.
  • a draw yarn has a very small diameter and thus excellent proppant dispersibility.
  • a PGA resin in a molten state and a PLA resin in a molten state are continuously discharged from a spinneret for composite fibers at a prescribed ratio so as to form a fibrous composite (discharge step).
  • the resulting fibrous composite may be held in an atmosphere at a prescribed temperature for a prescribed amount of time after being discharged as necessary (heat retaining step).
  • the fibrous composite is then cooled by a known cooling method such as air cooling to obtain an undrawn yarn (cooling step).
  • the undrawn yarn may be mass-produced and stored (storage step) and subjected to drawing processing as necessary to obtain a drawn yarn (drawing step).
  • the PGA resin and the PLA resin in the molten state can be prepared by melt-kneading using an extruder or the like.
  • the PGA resin and the PLA resin, in a pellet form or the like are each independently loaded into extruders 2 a and 2 b from raw material hoppers 1 a and 1 b, and the PGA resin and the PLA resin are melt-kneaded.
  • the melt temperature of the PGA resin is preferably from 200 to 300° C. and more preferably from 210 to 270° C.
  • the melt temperature of the PGA resin is less than the lower limit described above, the fluidity of the PGA resin is diminished, and the PGA resin is not discharged from the spinneret, which makes it difficult to form a fibrous composite.
  • the melt temperature exceeds the upper limit described above, the PGA resin tends to be discolored or pyrolyzed.
  • the melt temperature of the PLA resin is preferably from 170 to 280° C. and more preferably from 210 to 240° C.
  • the melt temperature of the PLA resin is less than the lower limit described above, the fluidity of the PLA resin is diminished, and the PLA resin is not discharged from the spinneret, which makes it difficult to form a fibrous composite.
  • the melt temperature exceeds the upper limit described above, the PLA resin tends to be pyrolyzed.
  • a stirrer, a continuous kneader, or the like can be used instead of an extruder, but it is preferable to use an extruder from the perspective that processing can be accomplished in a short period of time and that a smooth transition can be made to the subsequent discharge step.
  • the PLA resin in the molten state prepared as described above and the PGA resin in a molten state in an amount of 2 to 100 parts (preferably 3 to 100 parts and more preferably 5 to 80 parts) by mass per 1 part by mass of the D-lactic acid units in the PLA resin are discharged from a spinneret for composite fibers so as to form a fibrous composite comprising a phase containing the PGA resin in a molten state (called the “molten PGA resin phase” hereafter) and a phase containing the PLA resin in a molten state (called the “molten PLA resin phase” hereafter); the region formed by the molten PGA resin phase having a cross section with an area ratio of at most 50% (preferably at most 40%) (the region formed by the molten PGA resin phase more preferably has an area ratio of at most 50% (preferably at most 30%, more preferably at most 15%, and particularly preferably at most 10%)).
  • the PGA resin in a molten state is transferred to a spinneret 4 from the extruder 2 a while regulating the volume using a gear pump 3 a
  • the PLA resin in a molten state is transferred to the spinneret 4 from the extruder 2 b while regulating the volume using a gear pump 3 b.
  • the PGA resin and the PLA resin are then discharged from the hole of the spinneret 4 at a prescribed ratio and in an incompatible state to form a fibrous composite having the cross section and the side surface described above.
  • the content of the PGA resin in the component constituting the molten PGA resin phase is preferably at least 60 mass %, more preferably at least 80 mass %, even more preferably at least 95 mass %, and particularly preferably 100%.
  • the content of the molten PLA resin in the component constituting the PLA resin phase is preferably at least 60 mass %, more preferably at least 80 mass %, even more preferably at least 95 mass %, and particularly preferably 100%.
  • a conventionally known spinneret for composite fibers can be used as the spinneret 4 as long as a fibrous composite having the cross section and the side surface described above can be formed.
  • a concentric core-sheath type, an eccentric core-sheath type, a multicore type, a side-by-side type, a multiple-division type, a multilayer type, a radial type, or a composite type spinneret for composite fibers comprising two or more types thereof may be used as long as the region where the PGA resin in a molten state is discharged accounts for at most 50% in terms of area ratio (preferably at most 40%) in a hole.
  • the number of holes and the hole diameter of such a spinneret for composite fibers are not particularly limited.
  • the discharge temperature of the PGA resin and the PLA resin in a molten state is preferably from 210 to 280° C., and more preferably from 235 to 268° C.
  • spinneret temperature the discharge temperature of the composite in a molten state
  • the discharge temperature is less than the lower limit described above, the fluidity of the PGA resin and the PLA resin is diminished, and the resins are not discharged from the spinneret, which makes it difficult to form the fibrous composite.
  • the discharge temperature exceeds the upper limit described above, these resins tend to be prone to pyrolysis.
  • the fibrous composite discharged from the spinneret is preferably retained in a heat sleeve 5 set to a temperature of 110° C. or higher (preferably 120° C. or higher) as necessary. Consequently, an undrawn yarn with low orientation is obtained, which enables drawing at a high draw ratio. As a result, the single fiber fineness of the drawn yarn becomes low, which tends to result in a composite fiber with an even higher tensile strength.
  • the temperature inside the heat sleeve is preferably at most the melting point of the PGA resin.
  • the fibrous composite that is discharged from the spinneret When the fibrous composite that is discharged from the spinneret is held in an atmosphere at a temperature exceeding the melting point of the PGA resin immediately after being discharged, the fibrous composite tends to be prone to break in some parts during being taken up, which tends to lead to a lack of productivity.
  • the temperature inside such a heat sleeve, it is not absolutely necessary for the temperature to be constant, and the atmosphere may have a temperature distribution.
  • the temperature (temperature distribution) inside such a heat sleeve can be measured using an infrared laser thermometer or the like.
  • the fibrous composite formed in the discharge step is typically held in the heat sleeve 5 set to a prescribed temperature while being taken up.
  • the take-up rate (spinning rate) of the fibrous composite is not particularly limited, but it is particularly preferable to take up the fibrous composite at a take-up rate such that the mass per unit length of a single fiber constituting an undrawn yarn (hereafter called an “undrawn single fiber”) is 6 ⁇ 10 ⁇ 4 g/m or greater (and more preferably 13 ⁇ 10 ⁇ 4 g/m or greater).
  • the mass per unit length of the undrawn single fiber changes depending on factors such as the hole diameter of the spinneret and the discharge volume per hole of the spinneret, so the take-up rate is set while taking these factors into consideration so as to achieve the desired mass per unit length of the undrawn single fiber.
  • the fiber of the present invention having the side surface described above demonstrates excellent unwindability in the undrawn yarn
  • the fiber can be wound around a bobbin or the like or housed in a tow can for storage.
  • the undrawn yarn can be produced and stored in large quantities and can also be supplied stably, which enables the adjustment of the production of a drawn yarn.
  • the storage temperature is not particularly limited, but the undrawn yarn can be stably stored at 25 to 40° C.
  • a cooling device is necessary, which is not preferable from an economic standpoint. That is, in the method of producing the water-disintegrable composite fiber of the present invention, low-temperature storage is unnecessary, so it is possible to cut the production cost (storage cost) when producing a drawn yarn.
  • the agglutination of the undrawn composite fiber, which the PGA resin is exposed to the side surface of may occur, and it is not preferable for such composite fiber.
  • the storage time in the method for producing the water-disintegrable composite fiber of the present invention is not particularly limited, but the fiber can be stored, for example, for 24 hours or longer in an environment with a temperature of 30° C. and a relative humidity of 80% RH.
  • the water-disintegrable composite fiber of the present invention demonstrates excellent unwindability in the undrawn yarn
  • the undrawn yarn that is wound around a bobbin or the like or housed in a tow can for storage as described above can be drawn after being pulled out while being unwound.
  • a drawn yarn comprising a PGA resin phase and a PLA resin phase; the region formed by the PGA resin phase having a cross section with an area ratio of at most 50% (preferably at most 40%) (the region formed by the PGA resin phase more preferably has an area ratio of at most 50% (preferably at most 30%, more preferably at most 15%, and particularly preferably at most 10%); and the drawn yarn containing the PGA resin in an amount of from 2 to 100 parts by mass (preferably from 30 to 100 parts by mass and more preferably from 5 to 80 parts by mass) per 1 part by mass of the D-lactic acid units in the PLA resin.
  • the drawing temperature and draw ratio are not particularly limited and can be set appropriately in accordance with the desired physical properties and the like of the composite fiber, but the drawing temperature is preferably from 40 to 120° C., and the draw ratio is preferably from 2.0 to 6.0, for example.
  • the drawing method is not particularly limited, and a conventionally known fiber drawing method can be employed. For example, when drawing an undrawn yarn using the drawing device illustrated in FIG. 3 , an undrawn yarn is pulled out from a bobbin 14 via a feed roller 21 , and after the undrawn yarn is drawn using rollers 22 and 23 , the resulting drawn yarn is wound around a bobbin 25 .
  • the drawn yarn that is obtained in this way may be used directly as a long fiber or may be cut so as to form a staple fiber.
  • the cutting method is not particularly limited, and a publicly known cutting method used in the production method for a staple fiber can be employed.
  • Such a staple fiber has a small diameter and a large specific surface area and therefore tends to exhibit excellent proppant dispersibility when added to a well treatment fluid.
  • the PGA resin or the PLA resin in the water disintegrable composite fiber of the present invention in particular, the drawn yarn
  • hollow fibers can be obtained by removing the PGA resin from concentric core-sheath type ( FIG. 1A ), eccentric core-sheath type ( FIG. 1B ), and multicore type ( FIG. 1C ) water-disintegrable composite fibers.
  • the PLA resin it is possible to obtain a PGA resin single fiber having a smaller fiber diameter than the water-disintegrable composite fiber of the present invention.
  • a single fiber of the PGA resin or the PLA resin having a semicircular cross section can be obtained from a side-by-side type water-disintegrable composite fiber ( FIG. 1D )
  • a single fiber of the PGA resin or the PLA resin having a fan-shaped cross section can be obtained from a multiple-division type water-disintegrable composite fiber ( FIG. 1E )
  • a single fiber of the PGA resin or the PLA resin having a flat cross section can be obtained from a multilayer type water-disintegrable composite fiber ( FIG. 1F ).
  • a single fiber of the PGA resin having a radial cross section can be obtained by removing the PLA resin from a radial type water-disintegrable composite fiber ( FIG. 1G ).
  • Examples of methods for removing resins from the water-disintegrable composite fiber of the present invention include a method of separating the PGA resin phase and the PLA resin phase by peeling and a method of dissolving one of the resins by immersing the water-disintegrable composite fiber in a solvent that is a good solvent for one of the PGA resin or the PLA resin and a poor solvent for the other.
  • the solvent used in the dissolution method is not particularly limited.
  • the present invention will be described in further detail hereafter based on working examples and comparative examples, but the present invention is not limited to the following examples.
  • the physical properties of the resins and the properties of the undrawn yarn and staple fiber were measured with the following methods.
  • the melting point and the glass transition temperature of the resin were measured in a nitrogen atmosphere at a heating rate of 20° C./min using a differential scanning calorimeter (DSC; “TC-15” manufactured by Mettler-Toledo International Inc.).
  • DSC differential scanning calorimeter
  • the melt viscosity of the resin was measured using a capirograph equipped with capillaries (1 mm in diameter ⁇ 10 mm in length) (“Capirograph 1-C” manufactured by Toyo Seiki Seisakusho). Specifically, approximately 20 g of the resin was introduced into the capirograph set to a measurement temperature of 240° C. and was held for 5 minutes, and measurements were then performed under conditions with a shear rate of 122 sec ⁇ 1 .
  • the single fiber fineness was calculated from the following formula.
  • M is the absolute dry mass (g) of the drawn yarn
  • a staple fiber and deionized water were mixed in a vial with a volume of 50 ml so that the solid content concentration of the staple fiber was 2 mass %, and the resulting mixture was left to stand for 14 days in a gear oven set to 60° C. or 80° C. After being left to stand, the mixture was subjected to gravity filtration using filter paper, and the residue on the filter paper was dried at 80° C. The mass after drying was measured, and the mass loss was determined.
  • Pseudo-mud was prepared by adding 0.2 g of xanthan gum (“XCD-Polymer” manufactured by Telnite Co., Ltd.) and 2.0 g of starch (“Telpolymer DX” manufactured by Telnite Co., Ltd.) to 100 ml of a 10 mass % NaCl aqueous solution and stirring for 1 minute.
  • Staple fiber-dispersed pseudo-mud was prepared by adding 0.2 g of the staple fiber to the pseudo-mud and stirring for 1 minute.
  • Proppant/staple fiber-dispersed pseudo-mud was prepared by adding 6 g of a proppant (“Bauxite 20/40” manufactured by SINTEX Co., Ltd.) to the staple fiber-dispersed pseudo-mud and stirring for 1 minute.
  • a PGA/PLA composite undrawn yarn was produced by using the melt spinning device illustrated in FIG. 2 .
  • a temperature-controllable heat sleeve 5 with a length of 150 mm and an inner diameter of 100 mm was mounted beneath a spinneret 4 for composite fibers of the melt spinning device.
  • the cylinder temperature of the extruder 2 a was set to 215 to 250° C.
  • the adapter temperature, the gear pump temperature, and the spin pack temperature were set to 250° C.
  • the cylinder temperature of the extruder 2 b was set to 170 to 200° C.
  • the adapter temperature and the gear pump temperature were set to 200° C.
  • the spin pack temperature was set to 250° C.
  • the composite was passed through a heat sleeve 5 set to 120° C.
  • the fibrous PGA/PLA composite was then air-cooled, and the resulting PGA/PLA composite undrawn yarn was coated with an oiling agent for fibers (“Lurol”, made by the GOULSTON).
  • the yarn was taken up with a first take-up roller 7 at a circumferential speed of 1,000 m/min, and a core-sheath type PGA/PLA composite undrawn yarn (core part: PGA resin, sheath part: PLA resin) was wound around a bobbin 14 every 5,000 m via second to seventh take-up rollers 8 to 13 .
  • the content of the PGA resin in the resulting core-sheath type PGA/PLA composite undrawn yarn is 3.5 parts by mass per 1 part by mass of the D-lactic acid units in the PLA resin.
  • a bobbin around which the PGA/PLA composite undrawn yarn was wound was mounted on the drawing device illustrated in FIG. 3 , and this PGA/PLA composite undrawn yarn was unwound and drawn from the bobbin 14 via the feed roller 21 using a first heating roller 22 and a second heating roller 23 .
  • a core-sheath type PGA/PLA composite drawn yarn (core part: PGA resin, sheath part: PLA resin) was wound around a bobbin 25 via a third heating roller 24 .
  • the drawing temperature was set to 65° C., and the draw ratio was set to 2.2 times by adjusting the circumferential speeds of the first and second heating rollers.
  • the single fiber fineness of the resulting PGA/PLA composite drawn yarn was measured in accordance with the evaluation method described above. The results are shown in Table 1.
  • a PGA/PLA composite drawn yarn was cut using an EC cutter so as to produce a core-sheath type PGA/PLA staple fiber (core part: PGA resin, sheath part: PLA resin).
  • core part PGA resin
  • sheath part PLA resin
  • the mass loss and proppant dispersibility of the resulting PGA/PLA staple fiber were measured in accordance with the evaluation methods described above. These results are shown in Table 1.
  • the content of the PGA resin in the resulting core-sheath type PGA/PLA composite undrawn yarn is 5.7 parts by mass per 1 part by mass of the D-lactic acid units in the PLA resin.
  • a core-sheath type PGA/PLA composite drawn yarn (core part: PGA resin, sheath part: PLA resin) was then produced in the same manner as in Working Example 1 with the exception of changing the draw ratio to 2.5 times, and a core-sheath type PGA/PLA staple fiber (core part: PGA resin, sheath part: PLA resin) was further produced.
  • the single fiber fineness of the resulting PGA/PLA composite drawn yarn and the mass loss and proppant dispersibility of the PGA/PLA staple fiber were measured in accordance with the evaluation methods described above. These results are shown in Table 1.
  • the content of the PGA resin in the resulting core-sheath type PGA/PLA composite undrawn yarn is 10.5 parts by mass per 1 part by mass of the D-lactic acid units in the PLA resin.
  • a core-sheath type PGA/PLA composite drawn yarn (core part: PGA resin, sheath part: PLA resin) was then produced in the same manner as in Working Example 1 with the exception of changing the draw ratio to 2.5 times, and a core-sheath type PGA/PLA staple fiber (core part: PGA resin, sheath part: PLA resin) was further produced.
  • the single fiber fineness of the resulting PGA/PLA composite drawn yarn and the mass loss and proppant dispersibility of the PGA/PLA staple fiber were measured in accordance with the evaluation methods described above. These results are shown in Table 1.
  • the content of the PGA resin in the resulting core-sheath type PGA/PLA composite undrawn yarn is 17.9 parts by mass per 1 part by mass of the D-lactic acid units in the PLA resin
  • a core-sheath type PGA/PLA composite drawn yarn (core part: PGA resin, sheath part: PLA resin) was then produced in the same manner as in Working Example 1 with the exception of changing the draw ratio to 2.8 times, and a core-sheath type PGA/PLA staple fiber (core part: PGA resin, sheath part: PLA resin) was further produced.
  • the single fiber fineness of the resulting PGA/PLA composite drawn yarn and the mass loss and proppant dispersibility of the PGA/PLA staple fiber were measured in accordance with the evaluation methods described above. These results are shown in Table 1.
  • the content of the PGA resin in the resulting core-sheath type PGA/PLA composite undrawn yarn is 38.5 parts by mass per 1 part by mass of the D-lactic acid units in the PLA resin.
  • a core-sheath type PGA/PLA composite drawn yarn (core part: PGA resin, sheath part: PLA resin) was then produced in the same manner as in Working Example 4 with the exception of changing the draw ratio to 3.0 times, and a core-sheath type PGA/PLA staple fiber (core part: PGA resin, sheath part: PLA resin) was further produced.
  • the single fiber fineness of the resulting PGA/PLA composite drawn yarn and the mass loss and proppant dispersibility of the PGA/PLA staple fiber were measured in accordance with the evaluation methods described above. These results are shown in Table 1.
  • the content of the PGA resin in the resulting core-sheath type PGA/PLA composite undrawn yarn is 7.9 parts by mass per 1 part by mass of the D-lactic acid units in the PLA resin.
  • a core-sheath type PGA/PLA composite drawn yarn (core part: PGA resin, sheath part: PLA resin) was then produced in the same manner as in Working Example 4 with the exception of changing the draw ratio to 2.3 times, and a core-sheath type PGA/PLA staple fiber (core part: PGA resin, sheath part: PLA resin) was further produced.
  • the single fiber fineness of the resulting PGA/PLA composite drawn yarn and the mass loss and proppant dispersibility of the PGA/PLA staple fiber were measured in accordance with the evaluation methods described above. These results are shown in Table 1.
  • a PLA resin undrawn yarn was produced in the same manner as in Working Example 1 with the exception that a PGA resin was not used and that a spinneret for single fibers (hole size: 0.40 mm, 24 holes) was used as the spinneret 4 . An attempt was then made to produce a PLA resin drawn yarn by changing the draw ratio to 1.5 times, but the yarn broke when the yarn was drawn, and a PLA resin drawn yarn was not obtained.
  • a PLA resin undrawn yarn was produced in the same manner as in Working Example 4 with the exception that a PGA resin was not used and that a spinneret for single fibers (hole size: 0.40 mm, 24 holes) was used as the spinneret 4 .
  • the content of the PGA resin in the resulting core-sheath type PGA/PLA composite undrawn yarn is 1.2 parts by mass per 1 part by mass of the D-lactic acid units in the PLA resin.
  • a core-sheath type PGA/PLA composite drawn yarn (core part: PGA resin, sheath part: PLA resin) was then produced in the same manner as in Working Example 1 with the exception of changing the draw ratio to 1.3 times, and a core-sheath type PGA/PLA staple fiber (core part: PGA resin, sheath part: PLA resin) was further produced.
  • the single fiber fineness of the resulting PGA/PLA composite drawn yarn and the mass loss and proppant dispersibility of the PGA/PLA staple fiber were measured in accordance with the evaluation methods described above. These results are shown in Table 2.
  • the content of the PGA resin in the resulting core-sheath type PGA/PLA composite undrawn yarn is 1.5 parts by mass per 1 part by mass of the D-lactic acid units in the PLA resin.
  • Example 2 Example 3 D-form ratio 9.5 9.5 9.5 (%) of PLA Fiber structure Core-sheath Core-sheath Core-sheath type type type Core part: PGA Core part: PGA Core part: PGA Sheath part: Sheath part: Sheath part: PLA PLA PLA Area ratio (%) 25 35 50 of the PGA phase of the cross section Area ratio (%) 0 0 0 of the PGA phase of the side surface D-form content 7.1 6.2 4.8 (mass %) in the composite fiber PGA content 3.5 5.7 10.5 (parts by mass) per 1 part by mass of the D-lactic acid units in the PLA resin of the composite fiber Draw ratio 2.2 2.5 2.5 (times) Single fiber 2.0 1.3 1.4 fineness (denier) 60° C.
  • Example 6 D-form ratio 1.4 1.4 1.4 (%) of PLA Fiber structure Core-sheath Core-sheath Core-sheath type type type Core part: PGA Core part: PGA Core part: PGA Sheath part: Sheath part: PLA PLA PLA Area ratio (%) 20 35 10 of the PGA phase of the cross section Area ratio 0 0 0 (%) of the PGA phase of the side surface D-form content 1.1 0.9 1.3 (mass %) in the composite fiber PGA content 17.9 38.5 7.9 (parts by mass) per 1 part by mass of the D-lactic acid units in the PLA resin of the composite fiber Draw ratio 2.8 3.0 2.3 (times) Single fiber 1.5 1.5 1.9 fineness (denier) 60° C. mass 18.3 26.6 14.3 loss (%) 80° C. mass 88.5 91.4 81.5 loss (%) Pro
  • Example 2 Example 3 D-form ratio (%) of 9.5 9.5 1.4 PLA Fiber structure PLA PLA PLA Single fiber Single fiber Single fiber Area ratio (%) of the 0 0 0 PGA phase of the cross section Area ratio (%) of the 0 0 0 PGA phase of the side surface D-form content 9.5 9.5 1.4 (mass %) in the composite fiber PGA content (parts by 0 0 0 mass) per 1 part by mass of the D-lactic acid units in the PLA resin of the composite fiber Draw ratio (times) 1.5 1.3 1.7 Single fiber fineness (denier) — 3.5 — 60° C. mass loss (%) — 12.4 — 80° C.
  • a core-sheath type composite undrawn yarn (core part: PGA resin, sheath part: PLA resin) containing a prescribed amount of a PGA resin with respect to the D-lactic acid units in the PLA resin can be drawn at a ratio of 2 or more times and that the single fiber fineness of the core-sheath type composite drawn yarn (core part: PGA resin, sheath part: PLA resin) can be controlled to 2.0 denier or lower.
  • a core-sheath composite drawn yarn with such low fineness has excellent proppant dispersibility.
  • a water-disintegrable composite undrawn yarn which can be drawn at a high ratio. Accordingly, by drawing the water-disintegrable composite undrawn fiber of the present invention at a high ratio, it is possible to obtain a water-disintegrable drawn yarn with a small single fiber fineness (that is, a small diameter). Further, a the water-disintegrable composite staple fiber of the present invention formed by cutting the water-disintegrable drawn yarn of the present invention has a small diameter and a large specific surface area and therefore demonstrates excellent proppant dispersibility when added to a well treatment fluid.
  • the water-disintegrable composite staple fiber of the present invention is useful for applications to the drilling or completion field of oil and gas recovery from the perspective of productivity improvement, drilling cost reduction, reduction in damage to subterranean formation, and reduction in environmental burden.
  • the fiber is useful as an additive for improving the productivity of a subterranean formation with low permeability.
  • One method used for shale gas or shale oil recovery is hydraulic fracturing, and this fiber is useful at the time of hydraulic fracturing as an auxiliary material for efficiently transporting proppants such as sand or for efficiently refluxing a fluid containing proppants such as sand.
  • the fiber is useful as an auxiliary material for uniformly treating subterranean formation in acid treatment using hydrochloric acid or the like, which is typically used in drilling or completion of oil and gas recovery.
  • a water-disintegrable composite staple fiber it is possible to seal the subterranean formation through which fluids flow easily and to adjust the formation so that fluids flow at locations where fluid flow is desirable, and since the material decomposes at the time of production, this means that the productivity is not inhibited.
  • Such a sealing function can also be applied to improve the product recovery efficiency by temporarily sealing holes intentionally formed in subterranean formation, in particular, in production layers from which petroleum or gas can be obtained.
  • Other related applications for which the fiber is useful include applications for preventing the clogging of screens using disintegrability by utilizing the water-disintegrable composite fiber to form the cake layer formed during drilling, and applications for preventing lost circulation of water or mud into subterranean formation with high permeability or natural holes by adding a water-disintegrable composite fiber staple fiber to mud water for drilling.
  • the fiber In applications in which the fiber is added to mud for drilling, it has the effect of reducing the viscosity of mud and increasing the fluidity, by the releasing effect of acids released after decomposition of the fiber.
  • the water-disintegrable composite fiber to mud for drilling or completion, it is possible to reduce the amount of water or sand used, which makes it possible to reduce the drilling cost.
  • the water-disintegrable composite staple fiber has a disintegrating property, which yields the advantage that there is no damage to subterranean formation.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Textile Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Multicomponent Fibers (AREA)
  • Artificial Filaments (AREA)
US14/421,560 2012-09-14 2013-09-12 Water-disintegrable composite fiber and method for producing the same Abandoned US20150284879A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2012203035 2012-09-14
JP2012-203035 2012-09-14
PCT/JP2013/074730 WO2014042222A1 (ja) 2012-09-14 2013-09-12 水崩壊性複合繊維およびその製造方法

Publications (1)

Publication Number Publication Date
US20150284879A1 true US20150284879A1 (en) 2015-10-08

Family

ID=50278331

Family Applications (1)

Application Number Title Priority Date Filing Date
US14/421,560 Abandoned US20150284879A1 (en) 2012-09-14 2013-09-12 Water-disintegrable composite fiber and method for producing the same

Country Status (6)

Country Link
US (1) US20150284879A1 (de)
EP (1) EP2896726A4 (de)
JP (1) JP6021926B2 (de)
CN (1) CN104411868A (de)
CA (1) CA2881517C (de)
WO (1) WO2014042222A1 (de)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018017384A1 (en) * 2016-07-18 2018-01-25 Eastman Chemical Company Well treatment fiber delivery system
US10513902B2 (en) 2015-04-28 2019-12-24 Thru Tubing Solutions, Inc. Plugging devices and deployment in subterranean wells
US10513653B2 (en) 2015-04-28 2019-12-24 Thru Tubing Solutions, Inc. Flow control in subterranean wells
US10641057B2 (en) 2015-04-28 2020-05-05 Thru Tubing Solutions, Inc. Flow control in subterranean wells
US10767442B2 (en) 2015-04-28 2020-09-08 Thru Tubing Solutions, Inc. Flow control in subterranean wells
US10774612B2 (en) 2015-04-28 2020-09-15 Thru Tubing Solutions, Inc. Flow control in subterranean wells
US10851615B2 (en) 2015-04-28 2020-12-01 Thru Tubing Solutions, Inc. Flow control in subterranean wells
US11002106B2 (en) 2015-04-28 2021-05-11 Thru Tubing Solutions, Inc. Plugging device deployment in subterranean wells
US11022248B2 (en) 2017-04-25 2021-06-01 Thru Tubing Solutions, Inc. Plugging undesired openings in fluid vessels
US11293578B2 (en) 2017-04-25 2022-04-05 Thru Tubing Solutions, Inc. Plugging undesired openings in fluid conduits
US11851611B2 (en) 2015-04-28 2023-12-26 Thru Tubing Solutions, Inc. Flow control in subterranean wells

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101914494B1 (ko) * 2018-03-15 2018-11-02 광성지엠(주) 동공 탐사 및 복구 시스템

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060083917A1 (en) * 2004-10-18 2006-04-20 Fiber Innovation Technology, Inc. Soluble microfilament-generating multicomponent fibers
US20070224903A1 (en) * 2006-03-23 2007-09-27 Kimberly-Clark Worldwide, Inc. Absorbent articles having biodegradable nonwoven webs
US20120130024A1 (en) * 2009-08-06 2012-05-24 Kureha Corporation Polyglycolic acid-based fibers and method for producing same

Family Cites Families (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5284889A (en) * 1975-12-30 1977-07-14 Asahi Chemical Ind Surgical binding yarn
JPH07133511A (ja) 1993-11-10 1995-05-23 Toyobo Co Ltd 生分解性複合繊維及びそれを用いた不織布
US6579814B1 (en) * 1994-12-30 2003-06-17 3M Innovative Properties Company Dispersible compositions and articles of sheath-core microfibers and method of disposal for such compositions and articles
JPH09157954A (ja) * 1995-12-05 1997-06-17 Shimadzu Corp 帯電防止性繊維
JP2002500065A (ja) * 1998-01-06 2002-01-08 バイオアミド・インコーポレイテッド 生体吸収性繊維およびそれから製造される強化コンポジット
JP3474482B2 (ja) * 1999-03-15 2003-12-08 高砂香料工業株式会社 生分解性複合繊維およびその製造方法
US7070610B2 (en) * 2002-03-30 2006-07-04 Samyang Corporation Monofilament suture and manufacturing method thereof
US7275596B2 (en) * 2005-06-20 2007-10-02 Schlumberger Technology Corporation Method of using degradable fiber systems for stimulation
JP4650206B2 (ja) 2005-10-25 2011-03-16 チッソ株式会社 生分解性複合繊維、および、これを用いた繊維構造物と吸収性物品
US7604859B2 (en) * 2006-08-30 2009-10-20 Far Eastern Textile Ltd. Heat adhesive biodegradable bicomponent fibers
KR101577473B1 (ko) 2007-12-14 2015-12-14 쓰리엠 이노베이티브 프로퍼티즈 컴파니 다성분 섬유
FR2932498B1 (fr) * 2008-06-13 2010-09-10 Eric Alvarez Fibre composite thermofusible.
US20140377555A1 (en) * 2012-03-01 2014-12-25 Kureha Corporation Water-disintegrable composite fiber and method of producing the same

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060083917A1 (en) * 2004-10-18 2006-04-20 Fiber Innovation Technology, Inc. Soluble microfilament-generating multicomponent fibers
US20070224903A1 (en) * 2006-03-23 2007-09-27 Kimberly-Clark Worldwide, Inc. Absorbent articles having biodegradable nonwoven webs
US20120130024A1 (en) * 2009-08-06 2012-05-24 Kureha Corporation Polyglycolic acid-based fibers and method for producing same

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10767442B2 (en) 2015-04-28 2020-09-08 Thru Tubing Solutions, Inc. Flow control in subterranean wells
US10851615B2 (en) 2015-04-28 2020-12-01 Thru Tubing Solutions, Inc. Flow control in subterranean wells
US10513902B2 (en) 2015-04-28 2019-12-24 Thru Tubing Solutions, Inc. Plugging devices and deployment in subterranean wells
US10513653B2 (en) 2015-04-28 2019-12-24 Thru Tubing Solutions, Inc. Flow control in subterranean wells
US10641057B2 (en) 2015-04-28 2020-05-05 Thru Tubing Solutions, Inc. Flow control in subterranean wells
US10655427B2 (en) 2015-04-28 2020-05-19 Thru Tubing Solutions, Inc. Flow control in subterranean wells
US11851611B2 (en) 2015-04-28 2023-12-26 Thru Tubing Solutions, Inc. Flow control in subterranean wells
US10774612B2 (en) 2015-04-28 2020-09-15 Thru Tubing Solutions, Inc. Flow control in subterranean wells
US11427751B2 (en) 2015-04-28 2022-08-30 Thru Tubing Solutions, Inc. Flow control in subterranean wells
US11002106B2 (en) 2015-04-28 2021-05-11 Thru Tubing Solutions, Inc. Plugging device deployment in subterranean wells
US11242727B2 (en) 2015-04-28 2022-02-08 Thru Tubing Solutions, Inc. Flow control in subterranean wells
WO2018017384A1 (en) * 2016-07-18 2018-01-25 Eastman Chemical Company Well treatment fiber delivery system
US10465490B2 (en) 2016-07-18 2019-11-05 Eastman Chemical Company Well treatment fiber delivery system
US11022248B2 (en) 2017-04-25 2021-06-01 Thru Tubing Solutions, Inc. Plugging undesired openings in fluid vessels
US11293578B2 (en) 2017-04-25 2022-04-05 Thru Tubing Solutions, Inc. Plugging undesired openings in fluid conduits

Also Published As

Publication number Publication date
JP6021926B2 (ja) 2016-11-09
CN104411868A (zh) 2015-03-11
EP2896726A1 (de) 2015-07-22
EP2896726A4 (de) 2017-03-15
CA2881517C (en) 2016-06-14
JPWO2014042222A1 (ja) 2016-08-18
CA2881517A1 (en) 2014-03-20
WO2014042222A1 (ja) 2014-03-20

Similar Documents

Publication Publication Date Title
CA2881517C (en) Water-disintegrable composite fiber and method for producing the same
US20140377555A1 (en) Water-disintegrable composite fiber and method of producing the same
US20120130024A1 (en) Polyglycolic acid-based fibers and method for producing same
CA2868977C (en) Polyglycolic acid resin short fibers and well treatment fluid
WO2013161754A1 (ja) 坑井処理流体用ポリグリコール酸樹脂短繊維
JP6133847B2 (ja) ポリエステル樹脂組成物およびその成形体
US9902897B2 (en) Degradable fiber for use in well treatment fluid, method for manufacturing same, and well treatment method
US20120270048A1 (en) Biodegradable aliphatic polyester particles and production process thereof
JP5735536B2 (ja) ポリグリコール酸系樹脂未延伸糸、それを用いたポリグリコール酸系樹脂延伸糸、およびそれらの製造方法
JP5827550B2 (ja) 分解性樹脂から形成される成形品からなる層を積層してなる管状積層体、及びその製造方法
US9822298B2 (en) Method for treating a subterranean formation
JP2012251277A (ja) 生分解性脂肪族ポリエステル延伸糸およびその製造方法
JP2011245853A (ja) ポリグリコール酸系樹脂チューブの製造方法
JPWO2014077402A1 (ja) 生分解性モノフィラメントの製造方法
JP2010163722A (ja) 溶融紡糸方法
JPH03119109A (ja) ポリエステルの溶融紡糸法
JP2016060834A (ja) ポリ乳酸組成物からなる成形品の製造方法

Legal Events

Date Code Title Description
AS Assignment

Owner name: KUREHA CORPORATION, JAPAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:TAKAHASHI, TAKEO;CHIBA, YUKITOSHI;YAMAZAKI, MASAHIRO;AND OTHERS;SIGNING DATES FROM 20141225 TO 20150109;REEL/FRAME:034959/0009

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION