TW201741521A - Treating agent for polyolefin synthetic fiber, aqueous liquid thereof, method of treating polyolefin synthetic fiber, polyolefin synthetic fiber, and thermally-bonded nonwoven fabric - Google Patents

Abstract

The present invention provides a treating agent for polyolefin synthetic fiber, an aqueous liquid of the treating agent, a method of treating polyolefin synthetic fiber using the aqueous liquid, a polyolefin synthetic fiber having the treating agent adhered thereto, and a thermally-bonded nonwoven fabric made of the polyolefin synthetic fiber. The treating agent for polyolefin synthetic fiber is capable of keeping a good antistatic property or card passability and endows the obtained nonwoven fabric with a high hydrophilicity. Also, the nonwoven fabric can be adjusted to be weakly acidic. The treating agent for polyolefin synthetic fiber as used comprises: 0.3-18 mass% of a specific organic acid, 10-50 mass% of an alkyl phosphoric acid ester salt B having 4-11 carbon atoms, 10-50 mass% of an alkyl phosphoric acid ester salt C having 12-22 carbon atoms, and 25-65 mass% of a specific polyoxyalkylene derivative, based on a total of 100 mass%, and a specific aqueous liquid has a pH of 3 or above and less than 7.

Description

Treatment agent for polyolefin-based synthetic fiber, aqueous solution thereof, treatment method of polyolefin-based synthetic fiber, polyolefin-based synthetic fiber, and heat-bonded nonwoven fabric

The present invention relates to a treatment agent for polyolefin-based synthetic fibers, an aqueous solution thereof, a method for treating polyolefin-based synthetic fibers, a polyolefin-based synthetic fiber, and a thermo-bonded nonwoven fabric. In recent years, for non-woven fabrics for sanitary materials such as disposable diapers or menstrual sanitary napkins, a high degree of hydrophilicity or a weak acidity similar to that of the skin is required, and the treatment agent used in the manufacture of the nonwoven fabric is also required to impart a non-woven fabric to the obtained nonwoven fabric. This characteristic. The present invention relates to a treatment agent for a polyolefin-based synthetic fiber, an aqueous solution of the treatment agent, a method for treating a polyolefin-based synthetic fiber using the aqueous solution, and a polyolefin-based synthetic fiber to which the treatment agent is attached. And a heat-bondable nonwoven fabric made of the polyolefin-based synthetic fiber.

Conventionally, as a treatment agent for synthetic fibers, there has been proposed an alkyl phosphate ester salt (for example, see Patent Document 1), a polyoxyalkylene modified polyoxyl group having a specific functional group and a specific molecular weight, and A specific surfactant (for example, refer to Patent Document 2), a nonionic surfactant having a specific functional group, and an alkyl phosphate salt (see, for example, Patent Document 3). However, such conventional synthetic fiber treating agents have a problem in that even if these synthetic fiber treating agents are used for polyolefin-based synthetic fibers, good electric power or card passability cannot be maintained. Further, the obtained non-woven fabric is imparted with high hydrophilicity, and the non-woven fabric cannot be modified to be weakly acidic.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 8-188965

[Patent Document 2] Japanese Patent Laid-Open No. Hei 2-80672

[Patent Document 3] Japanese Patent Laid-Open No. 2001-3271

The problem to be solved by the present invention is to provide a treatment agent for a polyolefin-based synthetic fiber, an aqueous liquid of the treatment agent, a treatment method of a polyolefin-based synthetic fiber using the aqueous liquid, and a polyolefin-based synthesis to which the treatment agent is attached. The fiber and the polyolefin-based synthetic fiber heat-bondable nonwoven fabric, the polyolefin-based synthetic fiber treating agent can maintain good electrical conductivity or card passability, and impart high hydrophilicity to the obtained non-woven fabric, and Adjust the non-woven fabric to weakly acidic.

In order to solve the above problems, the inventors of the present invention have found that it is suitable to use a treating agent for polyolefin-based synthetic fibers which contains a specific four components in a specific ratio.

In other words, the present invention relates to a treatment agent for polyolefin-based synthetic fibers, which comprises the following organic acid in a ratio of 0.3 to 18% by mass, and the following alkyl phosphate salt in an amount of 10 to 50% by mass. B, the following alkyl phosphate salt C is contained in a ratio of 10 to 50% by mass, and a ratio of 25 to 65% by mass (100% by mass in total) is contained. Examples thereof include the following polyoxyalkylene alkyl derivative, and the pH of the aqueous liquid described below is 3 or more and less than 7. Further, the present invention relates to an aqueous liquid of the treating agent, a method for treating a synthetic fiber using the aqueous liquid, a polyolefin-based synthetic fiber to which the treating agent is adhered, and a heat-bondable nonwoven fabric made of the polyolefin-based synthetic fiber.

Organic acid: at least one selected from the group consisting of organic hydroxy acid, organic sulfonic acid and organic phosphoric acid

Alkyl phosphate salt B: alkyl phosphate salt having 4 to 11 carbon atoms

Alkyl phosphate salt C: alkyl phosphate salt having a carbon number of 12-22

Polyoxyalkylene derivative: a compound having ethylene oxide and/or propylene oxide added in a total amount of 5 to 100 moles per mole of aliphatic monohydric alcohol 1 mole having a carbon number of 22 to 50

Aqueous liquid: an aqueous liquid containing water in an amount of 400 to 100,000 parts by mass based on 100 parts by mass of the treating agent for polyolefin-based synthetic fibers

First, the treatment agent for polyolefin-based synthetic fibers of the present invention (hereinafter referred to as the treatment agent of the present invention) will be described. The treating agent of the present invention is obtained by containing a specific four components in a specific ratio as described above.

The organic acid used in the treatment agent of the present invention is at least one selected from the group consisting of organic hydroxy acid, organic sulfonic acid, and organic phosphoric acid. Specific examples of the organic hydroxy acid include glycolic acid, lactic acid, malic acid, tartaric acid, and citric acid. Examples of the organic sulfonic acid include p-toluenesulfonic acid and dodecylbenzenesulfonic acid. Examples thereof include octylphosphoric acid and dodecylphosphoric acid.

The alkyl phosphate salt B used in the treatment agent of the present invention is an alkyl phosphate salt having 4 to 11 carbon atoms, and specific examples thereof include a butyl phosphate salt, a hexyl phosphate salt, and an octyl phosphate ester. The salt, the thiol phosphate, the sulfhydryl phosphate, and the like are preferably an alkali metal salt having a carbon number of 6 to 8 such as an alkali metal hexyl phosphate or an alkali metal octyl phosphate.

The alkyl phosphate salt C used in the treatment agent of the present invention is an alkyl phosphate salt having 12 to 22 carbon atoms, and specific examples thereof include lauryl phosphate salt and tridecyl phosphate salt. , isotridecyl phosphate salt, tetradecyl phosphate salt, hexadecyl phosphate salt, octadecyl phosphate salt, octadecyl phosphate salt, isostearyl phosphate salt , a behenyl phosphate salt or the like, among which, a dodecyl phosphate alkali metal salt, a tridecyl phosphate alkali metal salt, an isotridecyl phosphate alkali metal salt, tetradecane is preferred. Carbon number of alkali metal phosphate, alkali metal hexadecyl phosphate, alkali metal octadecyl phosphate, alkali metal octadecyl phosphate, alkali metal salt of isostearyl phosphate It is an alkali metal salt of 12-18.

The alkyl phosphate salt B and the alkyl phosphate salt C are synthesized by reacting an aliphatic monohydric alcohol with a phosphorylating agent represented by phosphoric anhydride, and thereafter neutralizing with an alkali metal hydroxide. The aliphatic monohydric alcohol may be a single compound or a mixture of two or more kinds. Further, the alkali metal alkyl phosphate salt usually includes a mixture of a monoester, a diester, and a polymer containing a P-O-P bond, but the composition ratio thereof is not particularly limited. Further, the impurities contained in the synthetic raw material are allowed to be within the usual raw material standards. For example, various impurities and by-products such as a sodium component contained in potassium hydroxide and a heavy metal or an arsenic compound contained in a phosphoric acid anhydride which is one of phosphoric acid agents correspond to the impurities.

The polyoxyalkylene derivative used in the treating agent of the present invention is relative to An aliphatic monohydric alcohol having 1 to 50 carbon atoms is added to a compound having ethylene oxide and/or propylene oxide in a total amount of 5 to 100 moles. Specifically, examples of the polyoxyalkylene derivative include: relative to behenyl alcohol, tetracosyl alcohol, hexadecanol, octacosanol, triacontanol, and tetradecane. An aliphatic monohydric alcohol having 1 to 50 carbon atoms such as an alcohol, a tetradecanool or a frankanol, and an ethylene oxide and/or propylene oxide in a total amount of 5 to 100 moles. And the like, wherein, among them, an aliphatic monohydric alcohol having 1 to 40 carbon atoms, such as a hexadecanol, a octacosanol, a triacontanol or a tetradecyl alcohol, is preferably used. The ratio of ~60 moles is added to ethylene oxide and/or propylene oxide. In the polyoxyalkylene derivative, the addition form of ethylene oxide or propylene oxide is not particularly limited, and may be either block addition or random addition.

The treatment agent of the present invention contains the above organic acid in a ratio of 0.3 to 18% by mass, the alkyl phosphate salt B in an amount of 10 to 50% by mass, and the alkyl phosphate in an amount of 10 to 50% by mass. The salt C and the polyoxyalkylene derivative are contained in a ratio of 25 to 65 mass% (100 mass% in total), preferably containing an organic acid in a ratio of 0.3 to 18 mass%, and a mass of 15 to 45. The ratio of % contains the alkyl phosphate salt B, and the alkyl phosphate ester C is contained in a ratio of 15 to 45% by mass, and the polyoxyalkylene derivative is contained in a ratio of 25 to 65% by mass (100% by mass in total). Made.

In addition, as for the treatment agent of the present invention, the pH of the aqueous liquid containing water in an amount of 400 to 100,000 parts by mass based on 100 parts by mass of the treating agent for polyolefin-based synthetic fibers is 3 or more and less than 7 .

Next, the aqueous liquid of the treatment agent of the present invention (hereinafter referred to as the aqueous liquid of the present invention) will be described. The aqueous liquid of the present invention is an aqueous liquid containing water in an amount of 400 to 100,000 parts by mass based on 100 parts by mass of the treating agent of the present invention, and is an aqueous liquid having a pH of 3 or more and less than 7.

Examples of the water used in the aqueous liquid of the present invention include ion-exchanged water, distilled water, hard water, and soft water. Among them, ion-exchanged water, distilled water, and the like are preferable.

Next, a method of treating the polyolefin-based synthetic fiber of the present invention (hereinafter referred to as a treatment method of the present invention) will be described. In the treatment method of the present invention, the aqueous liquid of the present invention is adhered to the polyolefin-based synthetic fiber so as to be 0.1 to 1% by mass based on the polyolefin-based synthetic fiber according to the treatment agent of the present invention. As the adhesion method, a known method can be applied, and examples of the known method include a roll contact method, a spray method, a shower method, a dipping method, and the like. The step of attaching the aqueous liquid of the present invention may be any one of a spinning step, an extending step, and a finishing step. When the aqueous liquid of the present invention is adhered to the polyolefin-based synthetic fiber, other components than the treating agent of the present invention may be used in combination according to the purpose, and the other components are preferably used in combination as small as possible.

Next, the polyolefin-based synthetic fiber of the present invention (hereinafter referred to as the synthetic fiber of the present invention) will be described. The synthetic fiber of the present invention is a polyolefin-based synthetic fiber to which the treating agent of the present invention is attached.

Examples of the polyolefin-based synthetic fiber include polyolefin fibers such as polyethylene fibers, polypropylene fibers, and polybutene fibers; and composite fibers having a core-sheath structure, and either or both of the core and the sheath are polyolefins. Fiber composite fiber, for example, polyethylene/polypropylene composite fiber with polyethylene fiber, polyethylene/polyester composite fiber; or polyethylene/polypropylene composite fiber with parallel structure, polyethylene/polyester composite fiber Wait.

Finally, the heat-bondable nonwoven fabric of the present invention (hereinafter referred to as the nonwoven fabric of the present invention) will be described. The nonwoven fabric of the present invention is a thermo-bonded nonwoven fabric to which the treating agent of the present invention is attached.

As the heat-bondable nonwoven fabric, a nonwoven fabric obtained by an air through or a dot-bonding step can be used, and among them, it is preferably formed by hot air.

(cf. the efficacy of prior art)

According to the present invention, it is possible to maintain good electrical conductivity or card passability, and impart high hydrophilicity to the obtained non-woven fabric, and the nonwoven fabric can be adjusted to be weakly acidic.

[Examples]

Hereinafter, the examples and the like are exemplified to more specifically describe the constitution and effects of the present invention, but the present invention is not limited to the examples. In the following examples and comparative examples, the parts mean the parts by mass, and the other % means the mass%.

Test Category 1 (Preparation of a treatment agent for polyolefin-based synthetic fibers) ‧Example 1

2.8 g of 90% aqueous solution of lactic acid (A-1) shown in Table 1, 15.0 g of alkyl phosphate salt (B-1), 15.0 g of alkyl phosphate salt (C-1), and polyoxygen extension 17.5 g of the alkyl derivative (D-1) was mixed, and 949.7 g of water was added thereto, followed by stirring to obtain an aqueous dispersion, and a 5% aqueous solution of the treatment agent for polyolefin-based synthetic fibers of Example 1 was obtained.

‧Examples 2 to 9, Reference Examples 10 to 13, and Comparative Examples 1 to 7

In the same manner as in the case of Example 1, 5% aqueous solution of the treating agent for polyolefin-based synthetic fibers of Examples 2 to 9, Reference Examples 10 to 13, and Comparative Examples 1 to 7 was prepared. The contents of the treating agent for polyolefin-based synthetic fibers prepared in each of the above examples are collectively shown in Table 1.

In Table 1,

A-1: Lactic acid

A-2: citric acid

A-3: p-toluenesulfonic acid

A-4: Octyl phosphate

B-1: hexyl phosphate potassium salt

B-2: octyl phosphate potassium salt

B-3: octyl phosphate sodium salt

B-4: potassium butyl phosphate

B-5: thiol phosphate potassium salt

Rb-1: propyl phosphate potassium salt

C-1: potassium lauryl phosphate

C-2: octadecyl phosphate potassium salt

C-3: tetradecyl phosphate potassium salt

Rc-1: tetracosyl phosphate potassium salt

D-1: polyoxyethylene (10 mol) octadecyl ether

D-2: polyoxyethylene (25 mol) polyoxypropylene (25 mol) octadecyl ether

D-3: polyoxyethylene (35 mol) trioctadecyl ether

D-4: Polyoxyethylene (10 mol) tetracosyl ether

D-5: polyoxyethylene (10 mol) tetracosyl ether

D-6: polyoxyethylene (6 mole) octadecyl ether

D-7: Polyoxyethylene (80 mol) octadecyl ether

Rd-1: polyoxyethylene (10 mol) stearyl ether

Rd-2: polyoxyethylene (10 mol) hexadecyl ether

Rd-3: Polyoxyethylene (3 mole) octadecyl ether

Rd-4: Polyoxyethylene (60 mol) polyoxypropylene (60 mol) octadecyl ether

Test Category 2 (Adhesion and Evaluation of Treatment Agents for Polyolefin Synthetic Fibers) ‧Adhesion of polyolefin-based synthetic fiber treatment agent

The aqueous solution of the treatment agent for polyolefin-based synthetic fibers prepared in Test Category 1 was adhered to the sheath portion by polyethylene and the core portion was aggregated by the spray oil supply method so as to have the adhesion amount described in Table 2. Ester-based polyolefin composite fiber (denier of 2.2 cents, fiber The length of the dimension was 51 mm), and it was dried by a hot air dryer at 80 ° C for 1 hour to obtain a treated polyolefin-based synthetic fiber treated cotton. However, in Example 8, 100 parts of the treating agent for the polyolefin-based synthetic fiber prepared in Test Category 1 was used in combination with other components (E-1: 50% by mass in total). The modified base is a polyoxyalkylene group having a ratio of oxidized propyl unit/oxidized ethyl group unit of 50/50 (% by mass) and an average molecular weight of 5,000. The aqueous solution was sprayed with oil, and in Example 9, 100 parts of the treating agent for the polyolefin-based synthetic fiber prepared in Test Category 1 was used in combination with other components (E-2: octanoic acid) in a ratio of 10 parts. The aqueous solution of the potassium salt was sprayed with oil. Further, in Comparative Example 5, 100 parts of the treating agent for the polyolefin-based synthetic fiber prepared in Test Category 1 was used in combination with the other components (E) in an amount of 25 parts. -1) The aqueous liquid spray is supplied with oil.

‧Evaluation

The treated polyolefin-based synthetic fiber treated cotton obtained in the above section was evaluated for electric power and card passability as described below. The results are summarized in Table 2.

‧Evaluation of power generation

5 g of the above-mentioned treated polyolefin-based synthetic fiber treated cotton was subjected to humidity control for 24 hours in a thermostatic chamber at 20 ° C and 45% RH, and then the electric resistance (Ω) was measured using a resistance value measuring device, and evaluated according to the following evaluation criteria.

Benchmark for the evaluation of power generation

◎: Surface resistance is less than 1.0 × 10 ⁹ Ω

○: The surface resistance is 1.0 × 10 ⁹ Ω or more and less than 1.0 × 10 ¹⁰ Ω.

×: The surface resistance is 1.0 × 10 ¹⁰ Ω or more

‧Evaluation of carding passability

20 g of the above-mentioned treated polyolefin-based synthetic fiber treated cotton was subjected to humidity control for 24 hours in a thermostatic chamber at 20 ° C and 65% RH, and then supplied to a roll carding machine. The ratio of the discharge amount to the input amount was calculated and evaluated based on the following evaluation criteria.

Card evaluation criteria for passability

◎: The discharge amount is 80% or more

○: The discharge amount is 60% or more and less than 80%

×: The discharge amount is less than 60%

Test Category 3 (Production and Evaluation of Thermal Adhesive Nonwovens) ‧The production of hot sticky non-woven fabric

The treated polyolefin-based synthetic fiber treated cotton obtained in Test Category 2 was subjected to humidity control for 24 hours in a thermostatic chamber at 20 ° C and 65% RH, and then supplied to a roller card to prepare a basis weight of 20g/m ² cotton net. The obtained cotton web was subjected to hot air treatment at 140 ° C for 10 seconds to obtain a heat-bonded nonwoven fabric.

The thus obtained thermosetting nonwoven fabric was evaluated for initial hydrophilicity, durable hydrophilicity, moisture repellent property, and pH value of the nonwoven fabric as described below. The results are summarized in Table 2.

‧ Initial hydrophilicity assessment

24 small heat-resistant non-woven fabrics in a thermostatic chamber at 20 ° C and 60% RH The humidity control was carried out, and then placed on a horizontal plate, and 0.4 ml of water droplets were dropped from a height of 10 mm using a burette, and the time required until the water droplets were completely absorbed was measured, and evaluated according to the following evaluation criteria.

Initial hydrophilicity evaluation benchmark

◎: The time required until the water is permeable to less than 1 second

○: The time required until the water is permeable is 1 second or more and less than 2 seconds.

×: The time required until the water is permeable is 2 seconds or more

‧Evaluation of durable hydrophilicity

The above-mentioned thermo-bonded nonwoven fabric was cut into small pieces of 10 cm × 10 cm, and humidity control was performed for 24 hours in a thermostatic chamber at 20 ° C and 60% RH. A humidity-controlled non-woven fabric was placed on the five overlapping filter papers, and then a cylinder having an inner diameter of 1 cm was opened vertically at both ends of the non-woven fabric, and 0.9 ml of physiological saline was injected into the cylinder to 5 ml of saline. The measurement was performed at the time when it was completely absorbed by the nonwoven fabric. Thereafter, the nonwoven fabric was taken out and air-dried at 40 ° C for 90 minutes. The same operation was repeated three times in total, and the evaluation was performed based on the following evaluation criteria based on the third time.

Evaluation criteria for durable hydrophilicity

◎: The time required until the physiological saline is absorbed is less than 3 seconds.

○: The time required until the physiological saline is absorbed is 3 seconds or more and less than 5 seconds.

×: The time required until the physiological saline is absorbed is 5 seconds or longer.

‧Anti-wetting resistance assessment

The above-mentioned thermo-bonded nonwoven fabric was cut into small pieces of 10 cm × 10 cm, and humidity control was performed for 24 hours in a thermostatic chamber at 20 ° C and 60% RH. A non-woven fabric of 10 cm × 10 cm was cut out from the outermost non-woven fabric of a commercially available disposable diaper, and the above-mentioned small piece of 10 cm × 10 cm controlled by humidity was attached to the cut-off portion to prepare a moisture-proof evaluation sample. The anti-rewetting evaluation sample was horizontally placed with the mounted small piece facing upward, and a cylinder having an inner diameter of 6 cm was opened vertically at both ends of the small piece, and 80 ml of water was poured into the cylinder, and allowed to stand. The inside of the disposable diaper absorbs water for 5 minutes. Next, 15 sheets of 10 cm × 10 cm filter paper were placed on the mounted small pieces, and a 10 cm × 10 cm and 2.8 kg weight plate was placed on the filter paper and loaded for 2 minutes, after which the total of 15 pieces of filter paper overlapped was measured. The quality was calculated and the rate of increase of the mass was calculated and evaluated based on the following evaluation criteria.

Anti-humidification evaluation benchmark

◎: The quality increase rate is less than 1%

○: The mass increase rate is 1% or more and less than 2%.

×: The mass increase rate is 2% or more

‧pH evaluation

The above-mentioned thermo-bonded nonwoven fabric was subjected to humidity control for 24 hours in a thermostatic chamber at 20 ° C and 60% RH. The pH of the humidity-controlled non-woven surface was measured using a flat pH meter and evaluated on the basis of the following evaluation criteria.

pH evaluation benchmark

◎: The pH value of the non-woven fabric is 3 or more and less than 7

×: The pH of the non-woven fabric is less than 3 or 7 or more.

The results of Table 2 corresponding to Table 1 also show that according to the present invention, good electrical conductivity or card passability can be maintained, and the resulting non-woven fabric is imparted with a high degree of hydrophilicity, and the non-woven fabric can be adjusted to be weakly acidic. .

Claims (9)

A treatment agent for polyolefin-based synthetic fibers, which comprises the following organic acid in a ratio of 0.3 to 18% by mass, and the following alkyl phosphate salt B in an amount of 10 to 50% by mass, 10 to 50 The ratio of the mass% contains the following alkyl phosphate salt C, and the following polyoxyalkylene alkyl derivative (total 100% by mass) is contained in a ratio of 25 to 65 mass%, and the pH of the following aqueous liquid becomes 3 Above and less than 7; organic acid: at least one selected from the group consisting of organic hydroxy acid, organic sulfonic acid and organic phosphoric acid, alkyl phosphate salt B: alkyl phosphate salt having a carbon number of 4 to 11, alkyl phosphate Ester salt C: alkyl phosphate ester having a carbon number of 12 to 22, polyoxyalkylene alkyl derivative: 1 mol of aliphatic monohydric alcohol relative to carbon number 22 to 50, in total 5 to 100 mol A compound in which ethylene oxide and/or propylene oxide are added in a ratio, and an aqueous liquid: an aqueous liquid containing water in an amount of 400 to 100,000 parts by mass based on 100 parts by mass of the treating agent for polyolefin-based synthetic fibers. The treatment agent for polyolefin-based synthetic fibers according to claim 1, wherein the alkyl phosphate salt B is an alkali metal salt having 6 to 8 carbon atoms. The treatment agent for polyolefin-based synthetic fibers according to claim 1 or 2, wherein the alkyl phosphate salt C is an alkali metal salt having 12 to 18 carbon atoms. The treatment agent for polyolefin-based synthetic fibers according to any one of claims 1 to 3, wherein the polyoxyalkylene derivative is a total of 8 moles of aliphatic monohydric alcohol having a carbon number of 26 to 40. A ratio of ~60 moles is added to the compound of ethylene oxide and/or propylene oxide. The treatment agent for polyolefin-based synthetic fibers according to any one of claims 1 to 4, which contains an organic acid in a ratio of 0.3 to 18% by mass, and is contained in an amount of 15 to 45% by mass. The alkyl phosphate salt B contains an alkyl phosphate ester C in an amount of 15 to 45% by mass, and a polyoxyalkylene derivative in a proportion of 25 to 65% by mass (100% by mass in total). An aqueous liquid obtained by treating polyolefin-based synthetic fibers containing water in a ratio of 400 to 100,000 parts by mass based on 100 parts by mass of the treating agent for polyolefin-based synthetic fibers according to any one of claims 1 to 5; The aqueous liquid of the agent is characterized in that the pH is 3 or more and less than 7. A method for treating a polyolefin-based synthetic fiber, which is characterized in that the aqueous liquid of the claim 6 is adhered to the polyolefin-based synthetic fiber in an amount of 0.1 to 1% by mass based on the polyolefin-based synthetic fiber. A polyolefin-based synthetic fiber comprising the treating agent for a polyolefin-based synthetic fiber according to any one of claims 1 to 5. A heat-adhesive nonwoven fabric characterized in that the polyolefin-based synthetic fiber treatment agent according to any one of claims 1 to 5 is attached.