JP5978779B2 - Resin composition excellent in both oxidation heat resistance and discoloration resistance and synthetic resin fibers for sanitary products - Google Patents

Description

  The present invention relates to a resin composition excellent in both oxidation heat resistance and discoloration resistance and synthetic resin fibers for sanitary products, and more specifically, in the form of ultrafine fibers used for sanitary products such as masks. The present invention also relates to a resin composition excellent in both oxidation heat resistance and discoloration resistance and a synthetic resin fiber for hygiene products using the same.

The performance required for synthetic resin compositions such as polyethylene is diverse, but in the resin composition for ultrafine fibers used for sanitary goods such as masks, for which demand is particularly increasing in recent years, oxidation heat resistance and discoloration resistance are two types. There is a need for performance that is difficult to achieve.
That is, when these ultrafine fibers made of resin are stored in a warehouse as a flocculent lump during storage, there is a risk that the surface of the resin composition will be oxidized by contact with the air contained in the cotton to generate heat. Therefore, the resin composition for ultrafine fibers is required to satisfy the standard of oxidation heat resistance, which is an index that hardly generates heat in the presence of high temperature and oxygen.
On the other hand, as a sanitary product application, since the brown color impairs cleanliness, it is a whiter resin composition, that is, resistance to discoloration is required.

FIG. 1 attached to the present specification is a graph showing the oxidation heat resistance characteristics (OIT on the vertical axis) and the discoloration resistance characteristics (ΔYI on the horizontal axis) in relation to the values of the comparative examples of the present application. FIG. A larger OIT value is preferable because oxidation heat resistance is higher, and a smaller ΔYI value is preferable because discoloration is smaller. Therefore, it is required to obtain a resin composition in the upper left region (OIT ≧ 10.0, ΔYI ≦ 10.0) in the figure.
Conventionally, in order to obtain a resin composition having both oxidation heat resistance and discoloration resistance, an attempt has been made to search for various resin blends. However, in reality, a resin composition having both performances improved at the same time has been attempted. It was very difficult to get. Because, it is known from experience that oxidation heat resistance and discoloration resistance have a relationship of increasing to the right in the graph as a tendency. Therefore, when the amount of antioxidant is increased in order to improve oxidation heat resistance (vertical axis) This is because the coloring derived from the antioxidant occurs and the discoloration resistance is deteriorated (right side of the vertical axis).

For example, two kinds of antioxidants (phosphorus antioxidant and phenolic antioxidant) were used as antioxidants, and calcium stearate, which is a higher aliphatic group II metal salt, was combined as an inorganic compound. The resin composition is a combination of well-known resin compositions. As shown in A1 to A3 (Comparative Examples 1 to 3) in FIG. 1, even if the amount of the antioxidant is increased or decreased, the value of OIT, Neither the value of ΔYI can reach the target upper left region.
In order to obtain oxidation heat resistance, it is conceivable to use an antioxidant excellent in oxidation heat resistance. For example, an antioxidant having a phosphite structure and a phenol structure in the same molecule (for example, the trade name Sumilyzer (registered trademark) GP) is an antioxidant that is excellent in discoloration resistance and oxidation heat resistance even when used alone. Antioxidants known as agents.

For example, the following has been proposed as a resin composition in which other additives are added to the antioxidant.
For the purpose of providing a polyethylene resin composition that has sufficient stability against heat resistance and has excellent hue stability and is suitable for applications such as drawing tape and fiber drawing. 0.01 to 1 part by weight of an antioxidant having a phosphite structure and a hindered phenol structure in the same molecule corresponding to the component A of the present invention relative to 100 parts by weight of the resin, corresponds to the component D of the present invention Polyethylene containing 0.01 to 1 part by weight of a hydrotalcite-based compound and / or 0.01 to 1 part by weight of a Group II metal salt of a higher fatty acid corresponding to the C component of the present invention A resin composition has been proposed (Patent Document 1).

In addition, for the purpose of providing a polyolefin resin composition excellent in coloring resistance, thermal stability, and processability, and a molded article obtained using the resin composition, the present application is applied to 100 parts by weight of the polyolefin resin. 0.001 to 5 parts by weight of phosphites represented by a specific formula corresponding to the component A of the invention, 0.0001 to 0.5 parts by weight of an organic peroxide, and the neutralizing agent of the present invention. There has been proposed a polyolefin-based resin composition obtained by heat-melting and mixing calcium stearate corresponding to component C (Patent Document 2).
Another object of the present invention is to provide a polyolefin resin composition excellent in discoloration resistance, processing stability, antistatic properties, weather resistance and heat aging resistance against NOx gas, and a molded article comprising the resin composition. 0.001 to 5 parts by weight of phosphites represented by a specific formula corresponding to the component A of the present invention with respect to 100 parts by weight of the resin, 0.01 to 5 parts by weight of an amide antistatic agent, A polyolefin resin composition characterized by containing calcium stearate corresponding to the component C of the present invention as a neutralizing agent has been proposed (Patent Document 3).
In addition, a novel thermoplastic resin composition with improved processing stability, heat resistance coloration resistance and NOx coloration resistance, and thermoplastic resin by improving processing stability, heat resistance coloration resistance and NOx coloration resistance of the thermoplastic resin In order to provide a method for stabilizing the phosphite, a phosphite ester represented by a specific formula corresponding to the A component of the present invention, dimethyl succinate and 4-hydroxy-2,2, A thermoplastic resin composition containing a polymer of 6,6-tetramethyl-1-piperidineethanol and a hydrotalcite corresponding to the D component of the present invention has been proposed, and further an organic corresponding to the B component of the present invention. An example in which a phosphorus antioxidant is added in combination is also shown (Patent Document 4).

However, such a known resin composition certainly improves oxidation heat resistance and discoloration resistance to some extent, but satisfies the higher levels of oxidation heat resistance and discoloration resistance as intended by the present invention. A resin composition reaching the upper left region in the graph of 1 could not be obtained. Moreover, it was thought that it was difficult to obtain a resin composition reaching the upper left region even when looking at a change curve due to increase / decrease of each addition amount and a degree of performance improvement due to a difference in additives.
That is, A4 to A6 (Comparative Examples 4 to 6) in FIG. 1 of this application added calcium stearate (component C) to an antioxidant (component A) having a phosphite structure and a phenol structure in the same molecule. The values of the resin compositions are shown, and A7 to A9 (Comparative Examples 7 to 9) are resin compositions obtained by adding a hydrotalcite compound (D) in addition to the antioxidant (A) and calcium stearate (C). Indicates the value of the object.
A10 to A12 are examples in which a phosphorus antioxidant (B) and calcium stearate (C) are added to the antioxidant (A), and A13 to A14 are phosphorus antioxidants to the antioxidant (A). In this example, the agent (B) and the hydrotalcite compound (D) are added.
In both cases, both oxidation heat resistance (OIT) and discoloration resistance (ΔYI) are improved as compared with A1-3 (Comparative Examples 1 to 3). However, in order to improve oxidation heat resistance, the amount of antioxidant added is increased. If it increases, the discoloration resistance deteriorates, and it is clear that even if the change curve is seen, the target region in the upper left in the figure cannot be reached even if the antioxidant is increased or decreased.

  Therefore, other new antioxidants with improved both performances have been searched, but it is a compound that is difficult to use in terms of compound safety, a compound that is difficult to use in terms of cost, etc. There were restrictions on actual use.

  Therefore, there is no problem in terms of stability and cost of the compound, and it is difficult to achieve both of the high level of oxidation heat resistance and discoloration resistance required for the resin composition for ultrafine fibers used in sanitary goods such as masks. There has been a demand for a resin composition that satisfies the above requirements.

JP 2002-146121 A JP 2002-212347 A Japanese Patent Laid-Open No. 2003-231777 JP 2008-260929 A

  In view of the above circumstances, the object of the present invention is to use a resin composition excellent in both oxidation heat resistance and discoloration resistance performance, even if it is in the form of ultrafine fibers used for sanitary products such as masks. It is to provide synthetic resin fibers for hygiene products.

As mentioned above, there is no problem in the safety and cost of the compound, and it is possible to achieve both of the high level of oxidation heat resistance and discoloration resistance required for resin compositions for ultrafine fibers used in sanitary goods such as masks. Under the circumstances where a resin composition satisfying difficult performance has been demanded, the present inventor has also studied variously for many years to obtain a resin composition satisfying both high level of oxidation heat resistance and discoloration resistance, but it is quite practical. However, it was difficult to obtain a resin composition satisfying both performances.
However, it is the present invention that, as a result of an error in setting conditions during the experiment, the present inventors have surprisingly found that a resin composition having both performances improved simultaneously can be obtained.
That is, during various experiments, the master batch containing the component (A) and the component (C) was accidentally combined with the master batch containing the component (B) and the component (D) by mistake in the component (C). In the resin composition, it discovered that the resin composition of the new area | region which satisfy | fills both performance was obtained, and came to complete this invention. The four components, ie, the combination of the two kinds of specific antioxidants (A) and (B) and the combination of the two kinds of specific inorganic compounds (C) and (D) are essential, and (A ) By limiting the component content to a relatively low addition amount range, a split region that cannot be assumed from the combination of only three of the four components or the combination with other antioxidants. Thus, a resin composition having the following performance was obtained.
The components (A) and (B) are used as antioxidants, and the components (C) and (D) are used as neutralizers for polyethylene resins. ) Component antioxidants are known to be sufficiently effective when used alone, so they are usually used alone, and components (C) and (D) are also generally used for the same purpose. In general, it is an additive to be used, and it is usually selected according to the performance and cost suitable for the application.

  That is, according to the first invention of the present invention, (A) an antioxidant having a phosphite structure and a hindered phenol structure in the same molecule, and (B) a phosphorus-based antioxidant for the thermoplastic resin. , (C) a resin composition containing, as an essential component, a higher aliphatic periodic group II metal salt and (D) a hydrotalcite-based compound, the component (A) contained in the resin composition Provided is a resin composition excellent in both oxidation heat resistance and discoloration resistance, characterized in that the amount is 0.02 wt% or more and less than 0.1 wt%.

  According to the second invention of the present invention, in the first invention, the content of the component (B) in the resin composition is 0.02 wt% or more and 0.15 wt% or less, and the component (C) The content in the resin composition is 0.05% by weight or more and 0.15% by weight or less, and the content of the component (D) in the resin composition is 0.02% by weight or more and 0.1% by weight or less. A resin composition excellent in both oxidation heat resistance and discoloration resistance is provided.

  According to the third invention of the present invention, in the first or second invention, the ratio of the content of the component (A) and the content of the component (B) is 1: 0.5 to 1: 5. A resin composition excellent in both oxidation heat resistance and discoloration resistance is provided.

（ただし、式（Ｉ）及び式（ＩＩ）中、Ｒ_１、Ｒ_２、Ｒ_４及びＲ_５はそれぞれ独立に水素原子、炭素原子数１〜８のアルキル基を表し、Ｒ_３は水素原子又は炭素原子数１〜８のアルキル基を表し、Ｘは単なる結合又は−ＣＨＲ_６−基（Ｒ_６は水素原子、炭素数１〜８のアルキル基を示す）を表し、Ａ_１、Ａ_２は炭素数２〜８のアルキレン基を表し、Ａ_３は単なる結合又は炭素数２〜８のアルキレン基を表す。） According to the fourth aspect of the present invention, in any one of the first to third aspects, the component (A) is a compound represented by the following general formula (I) or general formula (II): A resin composition excellent in both oxidation heat resistance and discoloration resistance is provided.

(In the formulas (I) and (II), R ₁ , R ₂ , R ₄ and R ₅ each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R ₃ represents a hydrogen atom or Represents an alkyl group having 1 to 8 carbon atoms, X represents a simple bond or —CHR ₆ — group (R ₆ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms), and A ₁ and A ₂ represent carbon atoms. (A ₃ represents a simple bond or an alkylene group having 2 to 8 carbon atoms.)

  According to a fifth invention of the present invention, in any one of the first to fourth inventions, the thermoplastic resin is a polyethylene resin. An excellent resin composition is provided.

According to a sixth aspect of the present invention, in the fifth aspect, the polyethylene-based resin contains a high-density polyethylene resin having a density of 0.94 g / cm ³ or more and 0.96 g / cm ³ or less. A resin composition excellent in both oxidation heat resistance and discoloration resistance is provided.

According to the seventh aspect of the present invention, in any one of the first to sixth aspects, the discoloration resistance index (ΔYI) represented by the following formula (1) is 10.0 or less, and the following formula (2): An oxygen induction time (OIT) represented by the formula (1) is 10.0 or more, and a resin composition excellent in both oxidation heat resistance and discoloration resistance is provided.
Formula (1) ΔYI = NOI after exposure YI−initial value YI
Formula (2) OIT (min) = The temperature of the sample is increased to a predetermined temperature (210 ° C.) under a nitrogen atmosphere. When the temperature is stabilized, the sample is heated to oxygen, and then the sample starts to generate heat due to oxidation. Time required until the time (in the formula, YI is yellowness measured according to JIS K 7105-1981)

  Moreover, according to the 8th invention of this invention, the synthetic resin fiber for sanitary goods characterized by using the resin composition of the invention in any one of the 1st-7th is provided.

  The resin composition excellent in both the oxidation heat resistance and discoloration resistance of the present invention and the synthetic resin fiber for sanitary products can be used in the form of ultrafine fibers used for sanitary products such as a mask, It has the effect of being excellent in both discoloration resistance.

In the Example of this invention, it is the graph which showed the relationship between oxygen induction time (OIT) and a discoloration resistance index ((DELTA) YI). In the Example of this invention, it is the graph which showed the relationship between oxygen induction time (OIT) and a discoloration resistance index ((DELTA) YI).

The present invention relates to a thermoplastic resin (A) an antioxidant having a phosphite structure and a hindered phenol structure in the same molecule, (B) a phosphorus antioxidant, and (C) a higher aliphatic cycle. A resin composition containing, as essential components, a Group II metal salt and (D) hydrotalcite-based compound, wherein the content of the component (A) in the resin composition is 0.02% by weight or more. The present invention relates to a resin composition excellent in both oxidation heat resistance and discoloration resistance, characterized by being less than 0.1% by weight.
Moreover, this invention relates to the synthetic resin fiber for sanitary products which uses the said resin composition.
Hereinafter, the resin composition of the present invention, its components, and synthetic resin fibers will be described in detail.

1. Component (1) Thermoplastic Resin of Resin Composition The resin composition of the present invention contains a thermoplastic resin as an essential component.
Various thermoplastic resins can be used, for example, polyolefin resins such as polyethylene, polypropylene, polybutene, ethylene-α olefin copolymer, polyester resins such as polyethylene terephthalate, ABS resin, MBS resin. , Acrylic resin, polystyrene, polycarbonate, polyvinyl chloride, polyamide and the like. Among these, polyolefin resins are preferable, and polyethylene resins are particularly preferable.

The polyethylene resin used in the present invention includes a Ziegler-type catalyst, a Phillips-type catalyst (chromium-type catalyst), a polyethylene resin produced using a single-site catalyst, and a high-pressure radical method polyethylene resin. It is not limited to.
Moreover, it is preferable that the said polyethylene resin contains the high density polyethylene whose density is 0.94 g / cm < ³ > or more. Examples of the high-density polyethylene include an ethylene homopolymer, a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms, and the like. These polyolefin resins may be used alone or in combination of two or more.
Among them, as high-density polyethylene used for ultrafine fibers having a fiber system of several deniers, ethylene homopolymers having a density of 0.94 g / cm ³ or more and 0.96 g / cm ³ or less, ethylene and 1-butene, 1-pentene A copolymer with at least one selected from olefins such as 1-hexene and 1-octene is preferred. In addition, it is suitable that the melt flow rate at a temperature of 190 ° C. and a load of 2.16 kg is in the range of 10 to 50 g / 10 minutes, preferably 15 to 25 g / 10 minutes.
If the density is less than 0.940 g / cm ³ , the bulkiness (volume feeling) of the nonwoven fabric product may be reduced, and if it exceeds 0.960 g / cm ³ , the heat-fusibility between fibers deteriorates. Therefore, it is not preferable. On the other hand, if the melt flow rate is less than 10 g / 10 min, the spinnability will be difficult, and if it exceeds 50 g / 10 min, the strength of the fiber will be lowered, which is not preferable.
In the present invention, the melt flow rate (also referred to as MFR) is a value measured under each condition in accordance with JIS K 7210: 1999.

The method for producing high-density polyethylene in the present invention is produced by a gas phase polymerization method, a slurry polymerization method, a solution polymerization method, etc. substantially free of a solvent in the presence of a Ziegler type, a Philips type, a single site type catalyst, etc. Aliphatic hydrocarbons such as butane, pentane, hexane, and heptane, aromatic hydrocarbons such as benzene, toluene, and xylene, and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane with substantially no oxygen or water. It is produced in the presence or absence of an inert hydrocarbon solvent exemplified in the above.
The polymerization conditions are not particularly limited, but the polymerization temperature is usually 15 to 350 ° C., preferably 20 to 200 ° C., more preferably 50 to 110 ° C., and the polymerization pressure is usually normal pressure to 70 kg / cm in the case of the low to medium pressure method. ² G, preferably normal pressure to 20 kg / cm ² G, when the high-pressure process, usually less than 1500kg / cm ² G. In the case of the low intermediate pressure method, the polymerization time is usually 3 minutes to 10 hours, preferably about 5 minutes to 5 hours. In the case of the high pressure method, it is usually 1 minute to 30 minutes, preferably about 2 minutes to 20 minutes. In addition, the polymerization is not particularly limited to a single-stage polymerization method or a multi-stage polymerization method having two or more stages in which polymerization conditions such as hydrogen concentration, monomer concentration, polymerization pressure, polymerization temperature, and catalyst are different from each other.

  The thermoplastic resin of the present invention may be composed of two or more kinds of resins, and may contain, for example, a polyethylene resin and another resin. Examples of other resins include high-pressure radical polyethylene resin, copolymer of ethylene and α-olefin, copolymer of ethylene and polyunsaturated compound, copolymer of ethylene and vinyl ester, ethylene and α , Β-unsaturated carboxylic acid or a copolymer with a derivative thereof. The polyethylene resin may be acid-modified, for example, α, β-unsaturated fatty acid, alicyclic carboxylic acid, or a polymer graft-modified with these derivatives. The polyethylene resin also includes rubbery, fatty and waxy polymers. Furthermore, in this invention, the mixture which added synthetic rubber and the inorganic filler to these polyethylene resins can be used according to a use.

(2) Antioxidant (A) having a phosphite structure and a hindered phenol structure in the same molecule
The resin composition of the present invention is an antioxidant (A) having a phosphite ester structure and a hindered phenol structure in the same molecule (hereinafter also referred to as “antioxidant (A)” and “component (A)”). .) As an essential component.
Examples of the antioxidant (A) include compounds represented by the following general formula (I) or general formula (II), but the effects of the present invention are limited to the compounds shown in the specific examples. is not. The phosphite structure in the present invention refers to a structure in which a hydrogen atom of phosphorous acid P (OH) ³ is substituted with a hydrocarbon group. In addition, the hindered phenol structure in the present invention refers to a structure in which a hydrogen atom at positions 2 and 6 of phenol is substituted with a hydrocarbon group.

In formula (I) and formula (II), R ₁ , R ₂ , R ₄ and R ₅ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Here, typical examples of the alkyl group having 1 to 8 carbon atoms include, for example, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, t-butyl, t-pentyl. , Iso-octyl, t-octyl, 2-ethylhexyl and the like.

Especially, it is preferable that R < ₁ >, R < ₄ > is t-alkyl groups, such as t-butyl, t-pentyl, and t-octyl. R ₂ is preferably an alkyl group having 1 to 5 carbon atoms such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, t-butyl, t-pentyl and the like. In particular, methyl, t-butyl, and t-pentyl are preferable. R ₅ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, t-butyl, t-pentyl and the like. It is preferable.

The substituent R ₃ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and examples of the alkyl group having 1 to 8 carbon atoms include the same alkyl groups as described above. Preferably they are a hydrogen atom or a C1-C5 alkyl group, More preferably, they are a hydrogen atom or a methyl group.

X represents a simple bond or a —CHR ₆ — group (R ₆ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms). Here, X is preferably a simple bond, a methylene group or a methylene group substituted by methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, t-butyl, etc. It is preferable that

A ₁ and A ₂ represent an alkylene group having 2 to 8 carbon atoms. A ₃ represents a simple bond or an alkylene group having 2 to 8 carbon atoms. Typical examples of the alkylene group include ethylene, propylene, butylene, pentamethylene, hexamethylene, octamethylene, 2,2-dimethyl-1,3-propylene, and the like.

As an example of the compound represented by the general formula (I), 6- [3- (3-methyl-4-hydroxy-5-tert-butylphenyl) propoxy] -2,4,8,10-tetra-t- Butyl-dibenzo [d, f] [1,3,2] dioxaphosphine (R ₁ , R ₂ , R ₄ : t-butyl group, R ₃ : hydrogen, R ₅ : methyl group, X: simple bond , A ₁ : an alkylene group having 3 carbon atoms). An example of the compound represented by the general formula (II) is 6- {2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] ethoxy} -2,4,8. , 10-tetra-t-butyl-dibenzo [d, f] [1,3,2] dioxaphosphine (R ₁ , R ₂ , R ₄ : t-butyl group, R ₃ : hydrogen, R ₅ : Methyl group, X: simple bond, A ₂ , A ₃ : alkylene group having 2 carbon atoms).
Examples of commercially available compounds represented by the general formula (I) include “Sumilyzer (registered trademark) GP” manufactured by Sumitomo Chemical Co., Ltd.

  The blending amount of the antioxidant (A) in the present invention is 0.02% by weight or more and less than 0.1% by weight, preferably 0.03% by weight or more and less than 0.08% by weight, based on the whole resin composition. . If the blending amount of the component (A) is less than 0.02% by weight, the oxidation heat resistance may be poor. Moreover, there exists a possibility that discoloration resistance may become inferior that the compounding quantity of (A) component is 0.1 weight% or more.

(3) Phosphorous antioxidant (B)
The resin composition of the present invention contains a phosphorus-based antioxidant (B) (hereinafter, also referred to as “antioxidant (B)” or “component (B)”) as an essential component. The antioxidant (B) is a phosphorus antioxidant different from the antioxidant (A) (an antioxidant having a phosphite structure and a hindered phenol structure in the same molecule).

Specific examples of the antioxidant (B) include, for example, 3,5-di-t-butyl-4-hydroxybenzyl phosphite diethyl ester, bis (2,6-di-t-butyl-4-methylphenoxy) ) Diphosphospiroundecane, bis (stearyl) diphosphospiroundecane, cyclic netopentanetetraylbis (nonylphenylphosphite), bis (nonylphenylphenoxy) diphosphospiroundecane, 3,4,5,6-dibenzo-1 , 2-oxaphosphan-2-oxide, tris (2,4-di-tert-butylphenyl) phosphite, 2,4,6-tri-tert-butylphenyl-2-butyl-2-ethyl-1, 3-propanediol phosphite, 2,2′-methylenebis (4,6-di-t-butylphenyl) octyl phosphite, bis [ 2,4-bis (1,1-dimethylethyl) -6-methyl-phenyl] ethyl phosphite, bis (2,4-di-t-butylphenoxy) diphosphospiroundecane, trilauryl trithiophosphite, 1, 1,3-tris (2-methyl-4-di-tridecyl phosphite 5-t-butylphenyl) butane, 2,2′-ethylidenebis (4,6-di-t-butylphenyl) fluorophosphite, 4,4′-isopropylidene diphenol alkyl (C ₁₂ -C ₁₅ ) phosphite, 4,4′-butylidenebis (3-methyl-6-tert-butylphenyl) -di-tridecyl phosphite, diphenylisodecylphos Fight,

  Diphenyl mono (tridecyl) phosphite, tris- (mixed monononylphenyl and dinonylphenyl) phosphite, phenyl-bisphenol A pentaerythritol diphosphite, di (laurylthio) pentaerythritol diphosphite, tetrakis (2,6- Di-t-butyl-4-n-octadecyloxycarbonylethyl-phenyl) -4,4′-biphenylene-diphosphonite, tetrakis [2,6-di-t-butyl-4- (2,4′-di) -T-butylphenyloxycarbonyl) -phenyl] -4,4'-biphenylene-diphosphonite), tricetyltrithiophosphite, condensate of di-t-butylphenyl-m-cresylphosphonite and biphenyl, Cyclic butylethylpropanediol-2,4,6 Tri-butylphenyl phosphite, tris- [2- (2,4,8,10-tetrabutyl-5,7-dioxa-6-phosphodibenzo- {a, c} cyclohepten-6-yloxy) ethyl] amine, bis (Ethyl 3,5-di-t-butyl-4-hydroxybenzylphosphonate) calcium, 3,9-bis {2,4-bis (1-methyl-1-phenylethyl) phenoxy} -2,4,8 , 10-tetraoxa-3,9-diphosphaspiro [5,5] undecane and the like.

  Examples of commercially available antioxidants (B) include “Irgaphos (registered trademark) 168” and “Irgaphos (registered trademark) 12” manufactured by BASF Japan.

  The blending amount of the antioxidant (B) in the present invention is 0.02 wt% or more and 0.15 wt% or less, preferably 0.04 wt% or more and 0.12 wt% or less based on the whole resin composition. . When the blending amount of the component (B) is less than 0.02% by weight, there is a possibility that a synergistic effect cannot be obtained in improving the oxidation heat resistance in combination with the antioxidant (A). Moreover, when the compounding quantity of (B) component exceeds 0.15 weight%, there exists a possibility of blowing out on the product surface.

The ratio of the content of the component (A) to the content of the component (B) is preferably in the range of 1: 0.5 to 1: 5, more preferably 1: 1 to 1: 2.5, based on the weight. Range.
When the ratio of the content of the component (A) and the content of the component (B) exceeds the above range and the content of the component (A) increases or the content of the component (B) increases, the oxidation heat resistance improves. This is not preferable because the synergistic effect may be poor.

(4) Group II metal salt of higher aliphatic periodic table (C)
The resin composition of the present invention contains a higher aliphatic group II metal salt (C) (hereinafter also referred to as “neutralizing agent (C)” or “component (C)”) as an essential component. .

  Specific examples of (C) include calcium stearate, zinc stearate, aluminum stearate, magnesium stearate, calcium palmitate and the like. These higher fatty acid metal salts may be used alone or in combination of two or more, and the blending amount thereof is 0.05% by weight or more and 0.15% by weight or less in the resin composition. Preferably, it is 0.07 to 0.13% by weight. If the blending amount is less than 0.05% by weight, it is difficult to suppress discoloration resistance, and if it exceeds 0.15% by weight, it is difficult to disperse in the resin.

(5) Hydrotalcite compound (D)
The resin composition of the present invention contains the hydrotalcite compound (D) (hereinafter, also referred to as “neutralizing agent (D)” or “(D) component”) as an essential component.

The hydrotalcite compound is a hydrated basic carbonate of magnesium and aluminum. These may be either natural products or synthetic products. Natural product _has the chemical structure represented by _{Mg 6 Al 2 (OH) 16} CO 3 · 4H 2 O, while those as synthetic products differed in the ratio of Mg and Al, for example, the formula _Mg 4 _{A l2} (OH) ₁₂ CO ₃ .3H ₂ O, Mg ₅ Al ₂ (OH) ₁₄ CO ₃ .4H ₂ O, Mg ₁₀ Al ₂ (OH) ₂₂ (CO ₃ ) ₂ .4H ₂ O, Mg _4.5 Al ₂ Examples include (OH) ₁₃ CO ₃ .3.5H ₂ O. These hydrotalcite compounds may be used singly or in combination of two or more, and the blending amount thereof is 0.02 wt% or more and 0.1 wt% or less in the resin composition, Preferably it is 0.07 weight% or less. When the blending amount is less than 0.02% by weight, the oxidation heat resistance is insufficient, and when it exceeds 0.1% by weight, a problem occurs in dispersion in the resin.

2. Features of Resin Composition The resin composition of the present invention essentially comprises the four components (A), (B), (C), and (D), and the content of the component (A) is relatively low (resin 0.02% by weight or more and less than 0.1% by weight in the composition), and more preferably the content of the component (B) in the resin composition is 0.02% by weight or more and 0% or less. .15% by weight or less, (C) component content in resin composition is 0.05% by weight or more and 0.15% by weight or less, and (D) component content in resin composition is 0.02% by weight. More preferably, it is 0.1% by weight or less, more preferably, the ratio of the content of the component (A) and the content of the component (B) is in the range of 1: 0.5 to 1: 5. By doing so, it is possible to obtain a resin composition excellent in both oxidation heat resistance and discoloration resistance, which is an exquisite balance and conflicting performance. The
The resin composition of the present invention has a discoloration resistance index (ΔYI) represented by the following formula (1) of 10.0 or less and an oxygen induction time (OIT) represented by the following formula (2) of 10.0 or more. It is preferable that
Formula (1) ΔYI = NOI after exposure YI−initial value YI
Formula (2) OIT (min) = The temperature of the sample is increased to a predetermined temperature (210 ° C.) under a nitrogen atmosphere. When the temperature is stabilized, the sample is heated to oxygen, and then the sample starts to generate heat due to oxidation. Time required to start

In said formula (1), YI is the yellowness measured based on JISK7105-1981. The “initial value YI” is the initial YI of the adjusted sample, and the “YI after NOx exposure” is 7 days after the adjusted sample is left in a closed container and filled with NOx gas at a concentration of 500 ppm. Yellowness measured after exposure.
ΔYI is 10.0 or less, preferably 9 or less.
When ΔYI is greater than 10.0, the degree of discoloration is remarkable, which is not preferable for use as a sanitary material. The lower limit is not limited because ΔYI is preferably smaller. According to the present invention, a resin composition having a ΔYI value of at least 7.0 and 10.0 and an OIT value of 10.0 or more is used. Can be obtained.

Further, in the above formula (2), OIT (Oxigen induction time) is “from the time when the temperature of the sample is increased to a predetermined temperature (210 ° C.) under a nitrogen atmosphere and when the temperature is stabilized, the oxygen is switched to oxygen. Then, the time required until the sample starts to generate heat due to oxidation ”, and the“ time required until the sample starts to generate heat ”is, for example, measured by using a thermal analyzer. Time required to start.
OIT is 10.0 or more, preferably 15.0 or more, and more preferably 20.0 or more.
If the OIT is less than 10.0, the textile product is not preferable because the risk of spontaneous ignition due to oxidation heat generation increases.
Further, since the higher OIT is preferable, the upper limit is not limited. However, according to the present invention, a resin composition having an OIT value of at least 10.0 to 40.0 and a ΔYI value of 10.0 or less. Can be obtained.

3. Production method of resin composition The resin composition of the present invention contains, as an essential component, the four components (A), (B), (C) and (D) for the thermoplastic resin. Although it is a thing, the method currently performed can be used as a manufacturing method of a resin composition. There is no restriction | limiting in particular in the addition order of the said component.

4). Synthetic resin fibers for sanitary products The synthetic resin fibers for sanitary products of the present invention are produced using the resin composition of the present invention, but the production method is not particularly limited, and is a conventionally known method. Can be manufactured. For example, the polyethylene resin composition is extruded by an extruder equipped with a monofilament die, and once cooled, this is guided to a roller. After passing through the roller, it is heated by a heating tank and passed through a roller having a higher rotational speed than the roller. Due to the difference in the peripheral speed ratio between the two rollers, the filament can be stretched to produce a fiber.
The synthetic resin fiber for sanitary products can be an ultrafine fiber having a fiber diameter of several deniers. In this case, the fiber is suitable because it is excellent in oxidation heat resistance and discoloration resistance. When these ultrafine fibers made of resin are stored in a warehouse as a flocculent lump during storage, there is a risk that the surface of the resin composition will oxidize due to contact with the air contained in the cotton, and heat will be generated. The fiber of this type is resistant to heat generation in the presence of oxygen at a high temperature of about 210 ° C even when the fiber diameter is several deniers. In addition, it has excellent resistance to discoloration and is not easily yellowed. It is suitable for use.

5. Other Uses The resin composition of the present invention is particularly preferably used for bottle caps, white films, and the like that require discoloration resistance and oxidation heat resistance.
Specifically, a carbonated drink bottle cap etc. are illustrated and can be used suitably.

In the following, in order to more specifically and clearly describe the present invention, the present invention will be described in contrast to examples and comparative examples to demonstrate the rationality and significance of the requirements of the configuration of the present invention.
In each example and comparative example, evaluation methods of physical properties of the polymers used are shown below.

1. Evaluation method (1) Melt flow rate (MFR)
MFR was measured under each condition in accordance with JIS K 7210: 1999.
(2) Density A laminated film was punched out to a length of 2 mm, and measured at a test temperature of 23 ° C. in accordance with JIS K7112.

(3) ΔYI (discoloration resistance index)
I) Sample preparation for measurement The both ends of the test film as a sample were cut and adjusted so that the thickness accuracy was good (30 μ ± 10%). A film 50m having an adjusted thickness accuracy was wound into a cylindrical shape, and both ends were fastened and fixed with a hose band at a torque of 10 kg · cm to obtain a measurement sample.
II) Measurement of YI (initial value) One of the sample end faces adjusted in I) above was determined as the measurement surface, YI was measured with a color computer manufactured by Nippon Denshoku (model name: ZE2000), and this value was used as the YI initial value. .
III) Calculation of ΔYI In accordance with JIS L0855, the sample prepared in the above I) was allowed to stand in a sealed container, filled with 500 ppm of NOx gas, and exposed at 23 ° C. for 7 days. A sample was taken out immediately after the exposure period, YI was measured by the same method as in II) above, and ΔYI was calculated by the following equation (1).
ΔYI = YI after exposure to NOx−initial value YI (1)

(4) Oxygen induction time (OIT)
The measurement was performed under the following conditions using a DSC7020 thermal analyzer manufactured by SII Nano Technology.
Measurement temperature: 210 ° C
Temperature increase rate: 20 ° C./min Nitrogen flow rate: 50 ml / min Oxygen flow rate: 50 ml / min Sample: 30 μm film Sample weight: 15 mg
When the temperature is raised in a nitrogen atmosphere until it reaches a predetermined temperature (210 ° C.) and the temperature is stabilized, when the temperature is switched to oxygen, the sample starts to generate heat due to oxidation.
The required time from the start of switching to oxygen to the start of exotherm was defined as the oxygen induction time (OIT).

2. Component (1) Thermoplastic resin As a thermoplastic resin, "Novatec (registered trademark) HD: HE490" manufactured by Nippon Polyethylene, which is a high-density polyethylene, no additive powder during polymerization (the additive collected at the time of production is not blended) Polyethylene powder), MFR (conforming to JIS K6922-2): 22 g / 10 min, density (conforming to JIS K7112): 0.956 g / cm ³ was used.

(2) Antioxidant The antioxidant (A), an antioxidant having a phosphite ester structure and a hindered phenol structure in the same molecule, phosphorous antioxidant manufactured by Sumitomo Chemical Co., Ltd., trade name “Sumilyzer” GP "was used.
As a phosphorus-based antioxidant which is the antioxidant (B), a phosphorus-based antioxidant manufactured by BASF Japan, trade name “Irgaphos 168” was used.
In addition, as the antioxidant (E), a phenolic antioxidant manufactured by BASF Japan, trade name “Irganox 1076” was used.

(3) Neutralizer As a neutralizer (C), a higher aliphatic periodic table Group II metal salt, calcium stearate manufactured by NOF Corporation, trade name “Calcium stearate G” was used.
As a hydrotalcite compound which is a neutralizing agent (D), Kyowa Chemical Co., Ltd. hydrotalcite, a brand name "DHT-4A" was used.

3. Examples and Comparative Examples (Examples 1-8 and Comparative Examples 1-17)
(1) Preparation of resin composition Weigh the specified amount of additives shown in Tables 1 to 3 to the high-density polyethylene powder as a base, and stir for 3 minutes with a Henschel mixer so that the polyethylene and additive are homogeneously mixed. It was adjusted. (The numbers in the table indicate the weight percent of each additive in the composition)
(2) Pelletization In order to use the additive-added polyethylene powder prepared above in a film molding machine, extrusion granulation was performed using the extruder under the following conditions to obtain pellets.
Extruder: Modern machinery 50mmφ (single shaft)
L / D: 24
Screw compression ratio: 2.5 (3-stage full flight type)
Extruder temperature setting (℃)
Cylinder 1: 140
Cylinder 2 to Cylinder 3: 160
Extruder head to die: 140
Nozzle: 3mmφ (hole diameter) x 8 (number of holes)
Screen mesh configuration: 100/120/100
Extrusion amount: 22Kg / Hr
Strand cooling: Water cooling (room temperature)
Pelletization: In-house pelletizer (3) Film formation The pellet obtained under the above conditions was formed into a film under the following conditions to obtain an evaluation sample.
Equipment: Mitsubishi Heavy Industries 50mmφT die film molding equipment L / D: 24 Screw compression ratio: 2.8 (3-stage full flight type)
T die: Die width 300mm Lip width 1.0mm (Coat hanger type)
Extruder temperature setting (℃)
Cylinder 1: 180
Cylinder 2 to Cylinder 3: 200
Adapter, die 1 to die 3: 200
Film cooling method: chill roll + air knife chill roll temperature setting (° C): 80
Film thickness: 30 μm

4). Evaluation Hereinafter, the description of the present embodiment and the comparative example will be described based on the graphs shown in FIGS.
In Examples and Comparative Examples, the relationship between oxygen induction time (OIT) and discoloration resistance index (ΔYI) is graphed and shown in FIG. 1 and FIG.
FIG. 1 is a graph showing the relationship between OIT and ΔYI in Examples 1-8 and Comparative Examples 1-17. FIG. 2 is a graph showing the values of OIT and ΔYI in Example 1, Comparative Example 3, Comparative Example 11 and Comparative Example 13.
Comparative Examples 1 to 3 are examples in which the combination of antioxidants is not the (A) component and the (B) component of the present invention, but the (B) component and another antioxidant (E). In this example, only one component (C) was used as the (neutralizing agent), and the addition amount of the antioxidant (E) was changed to 0.1% by weight, 0.05% by weight, and 0.025% by weight, respectively. It is an example. As shown in the plots of A1 to A3 in FIG. 1, the results of the resin composition of this system have a low level of oxidation heat resistance and unfavorable discoloration resistance.
Comparative Examples 4 to 6 are examples using only one component (A) as an antioxidant and one component (C) as a neutralizer. Compared with Comparative Examples 1 to 3, the level of oxidation heat resistance and discoloration resistance is slightly improved, but the target region (ΔYI is 10.0 or less and OIT is 10.0 or more) has not been reached. .
Comparative Examples 7 to 9 are examples using one (A) component as an antioxidant and two (C) and (D) components as a neutralizing agent. When the addition amount of the antioxidant (A) is 0.05% by weight and 0.1% by weight, the OIT which is the target of oxidation heat resistance sufficiently satisfies 10.0 or more, but the color change resistance is the target ΔYI. It did not reach 10.0 or less.
Comparative Examples 10 to 12 are examples in which two types of component (A) and component (B) were used in combination as an antioxidant, and one component (C) was used as a neutralizing agent. Although the level of oxidation heat resistance is improved, the discoloration resistance is still inferior, and the target area is not reached.
Comparative Examples 13 to 14 are examples in which two components (A) and (B) are used in combination as an antioxidant, and one component (D) is used as a neutralizing agent. Although this also improves the level of oxidation heat resistance, the discoloration resistance is inferior, and even if the amount of component (A) is added, the target area is not reached.
Even when at least Comparative Examples 10 to 12 (ABC) and Comparative Examples 13 to 14 (ABD) essential for the three components are seen, the four component essential systems (A), (B), (C), and (D) of the present invention are used. However, it cannot be expected to have a significant effect as shown below.
Comparative Examples 15 to 17 use two types of components (A) and (B) as antioxidants and two types of components (C) and (D) as neutralizers. It is an example which shows the case where quantity is higher than the range specified by this invention. As shown in the graph, the resin composition to which component (A) is added in an amount of 0.15 wt% to 0.3 wt% has a high oxidation heat resistance value but a high level of discoloration resistance (ΔYI). The target area of the invention (ΔYI is 10.0 or less and OIT is 10.0 or more) cannot be reached.
On the other hand, the effects of the present invention are as shown in Examples 1 to 8 (B1 to B8 in the figure).
FIG. 2 is a graph showing the values of OIT (left side) and ΔYI (right side) in Example 1 (B1), Comparative Example 5 (A5), Comparative Example 11 (A11), and Comparative Example 13 (A13). It is a figure. The OIT (oxidation heat resistance) shown on the left side is preferably higher, and the ΔYI (color change) shown on the right side is preferably smaller.
From FIG. 2, it is clearly shown that both the OIT and ΔYI of the system of the present invention, which is essential for the four components, are significantly better than the combination of only two or three of the four components. Has been. In particular, compared with the effect predicted from the results of A11 of the (A) + (B) + (C) component and A13 of the (A) + (B) + (D) component, (A) + ( It is clearly shown that the effect of B) + (C) + (D) is specifically good.
Therefore, by making the four components (A), (B), (C), and (D) of the present invention essential, and making the content of the component (A) a specific range, ΔYI is 10.0 or less and OIT It was confirmed that it was possible to obtain a resin composition in a new region having both oxidation heat resistance and discoloration resistance of 10.0 or more.

As described above, from the results shown in Tables 1 to 3, when Examples 1 to 8 and Comparative Examples 1 to 17 are compared, the specific matter of the resin composition of the present invention is “(A) An antioxidant having a phosphite structure and a hindered phenol structure in the same molecule, (B) a phosphorus-based antioxidant, (C) a higher aliphatic periodic group II metal salt, and (D) hydrotal It is a resin composition containing the four components of the site compound as essential, and the content of the component (A) in the resin composition is 0.02 wt% or more and less than 0.1 wt% ” What was shown to Comparative Examples 1-17 by the resin composition which is not satisfy | filled did not become what has both oxidation heat resistance and discoloration resistance.
Compared with these comparative examples, it was confirmed that the resin composition according to the present invention has both oxidation heat resistance and discoloration resistance, as shown in Examples 1 to 8.

The resin composition and the synthetic resin fiber for sanitary products of the present invention are excellent in both oxidation heat resistance and discoloration resistance even if they are in the form of ultrafine fibers used for sanitary products such as masks. In particular, it can be particularly suitably used for ultrafine fibers used in sanitary products such as a fiber having a diameter of several deniers, which requires resistance to discoloration simultaneously with oxidation heat resistance, and is extremely useful industrially.

Claims (7)

For thermoplastic resins, (A) an antioxidant having a phosphite structure and a hindered phenol structure in the same molecule, (B) a phosphorus antioxidant, and (C) a higher aliphatic periodic table II A resin composition containing, as an essential component, a group 4 metal salt and (D) a hydrotalcite-based compound, the content of the component (A) in the resin composition is 0.02 wt% or more and 0.1 wt% The content of the component (B) in the resin composition is 0.02% by weight or more and 0.15% by weight or less, and the content of the component (C) in the resin composition is 0.05% by weight or more and 0.005% or less. 15% by weight or less, and (D) component content in the resin composition is 0.02% by weight to 0.1% by weight. Composition. The oxidation heat resistance and discoloration resistance according to claim 1, wherein the ratio of the content of the component (A) and the content of the component (B) is in the range of 1: 0.5 to 1: 5. Resin composition excellent in both performances. (A) Component is the compound shown by the following general formula (I) or general formula (II), The resin excellent in both the oxidation heat resistance and discoloration-resistant performance of Claim 1 or 2 characterized by the above-mentioned Composition.

(In the formulas (I) and (II), R ₁ , R ₂ , R ₄ and R ₅ each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R ₃ represents a hydrogen atom or Represents an alkyl group having 1 to 8 carbon atoms, X represents a simple bond or —CHR ₆ — group (R ₆ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms), and A ₁ and A ₂ represent carbon atoms. (A ₃ represents a simple bond or an alkylene group having 2 to 8 carbon atoms.) The resin composition excellent in both oxidation heat resistance and discoloration resistance performance according to any one of claims 1 to 3 , wherein the thermoplastic resin is a polyethylene resin. It said polyethylene resin, the oxidation heat and discoloration of both performance according to claim 4, characterized in that it contains a density 0.94 g / cm ³ or more 0.96 g / cm ³ or less of a high-density polyethylene resin Excellent resin composition. The discoloration resistance index (ΔYI) represented by the following formula (1) is 10.0 or less, and the oxygen induction time (OIT) represented by the following formula (2) is 10.0 or more. Item 6. A resin composition excellent in both oxidation heat resistance and discoloration resistance according to any one of Items 1 to 5 .
Formula (1) ΔYI = NOI after exposure YI−initial value YI
Formula (2) OIT (min) = The temperature of the sample is increased to a predetermined temperature (210 ° C.) under a nitrogen atmosphere. When the temperature is stabilized, the sample is heated to oxygen, and then the sample starts to generate heat due to oxidation. Time required until the time (in the formula, YI is yellowness measured according to JIS K 7105-1981) A synthetic resin fiber for sanitary products, comprising the resin composition according to any one of claims 1 to 6 .

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