JP7166069B2 - Method for suppressing yellowing of resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for suppressing yellowing of a resin caused by water, heat, light, etc. due to long-term use.

When exposed to harsh conditions or used for a long period of time, resins such as plastics are degraded by water, heat, sunlight, and the like, resulting in deterioration of mechanical properties and yellowing. Therefore, resins are mixed with various stabilizers. Heat stabilizers such as phenol compounds and phosphorus compounds, antioxidants such as amine compounds and phenol compounds, and light stabilizers such as benzotriazole compounds and benzophenone compounds are commonly used as stabilizers. . However, even when these stabilizers are blended, deterioration occurs depending on the conditions and duration of use, and in particular, it has been difficult to highly suppress yellowing due to heat history.

Polysilane, on the other hand, is usually a pale yellow powder and is known as a resin modifier. Japanese Patent Application Laid-Open No. 2003-268247 (Patent Document 1) describes the addition of polysilane to suppress the deterioration of mechanical properties such as tensile strength when additives such as flame retardants and reinforcing agents are added to resins. Formulating as a modifier is disclosed.

Japanese Patent Application Laid-Open No. 2003-277756 (Patent Document 2) discloses a method of adding polysilane to a thermoplastic resin or thermosetting resin as a halogen-free and highly safe flame retardant. WO 2015/064394 (Patent Document 3) describes polysilane as a compounding agent for suppressing deterioration of a polyolefin molded article such as a pipe due to hot water circulating therein and a decrease in mechanical properties such as elongation at break. is disclosed. Furthermore, Japanese Patent Application Laid-Open No. 2016-204620 (Patent Document 4) discloses polysilane as a crystal nucleating agent for suppressing the growth of spherulites in a molded body made of polyolefin.

Japanese Patent Application Laid-Open No. 2003-268247 JP-A-2003-277756 WO2015/064394 JP 2016-204620 A

However, the above-mentioned patent documents neither describe nor suggest the relationship between polysilane and resin yellowing.

An object of the present invention is to provide a method for suppressing yellowing of thermoplastic resins.

As a result of intensive studies to achieve the above object, the inventors of the present invention have unexpectedly found that yellowing of thermoplastic resins can be suppressed by blending polysilane, which is usually a light yellow powder, into resins. We have completed the present invention.

That is, the present invention is a method for suppressing yellowing of a resin, which comprises blending a polysilane with a thermoplastic resin and melt-kneading the mixture. The polysilane preferably has a weight-average molecular weight of 400 to 50,000, and the polysilane preferably has at least one structural unit among the structural units represented by the following formulas (1) and (2). and/or cyclic polysilane.

(wherein R ¹ to R ³ are the same or different and represent a hydrogen atom, a hydroxyl group, an organic group or a silyl group).

The thermoplastic resin is preferably at least one selected from the group consisting of olefin resins, polyester resins and polycarbonate resins. In the present invention, the thermoplastic resin and the polysilane are preferably blended at a weight ratio of the former/the latter=99.95/0.05 to 90/10.

In the specification and claims of the present application, the number of carbon atoms in a substituent may be indicated by C ₁ , C ₆ , C ₁₀ or the like. That is, for example, an alkyl group having 1 carbon atom is indicated by "C ₁ alkyl", and an aryl group having 6 to 10 carbon atoms is indicated by "C _6-10 aryl".

In the present invention, polysilane can be added to a thermoplastic resin to suppress yellowing of the thermoplastic resin. In particular, yellowing of the thermoplastic resin can be effectively suppressed by adding polysilane to the thermoplastic resin, which is susceptible to heat history. In addition, it has a large effect of suppressing yellowing, and even if it is blended in a small amount, yellowing of the thermoplastic resin can be suppressed.

Polysilane is not particularly limited as long as it is a chain (straight or branched), cyclic or network compound having Si—Si bonds. Polysilane usually has at least one structural unit among the structural units represented by the following formulas (1) and (2). The molecular structure of polysilane is preferably chain (linear or branched) or cyclic.

(In the formula, R ¹ to R ³ are the same as above).

In formulas (1) and (2), the organic groups represented by R ¹ to R ³ include hydrocarbon groups and ether groups corresponding to these hydrocarbon groups. Examples of the hydrocarbon groups include alkyl groups, alkenyl groups, cycloalkyl groups, cycloalkenyl groups, aryl groups, and aralkyl groups. Examples of the ether group include an alkoxy group, a cycloalkyloxy group, an aryloxy group and an aralkyloxy group. Usually, the organic groups are often hydrocarbon groups such as alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups and aralkyl groups. Hydrogen atoms, hydroxyl groups, alkoxy groups, silyl groups and the like represented by R ¹ to R ³ are often substituted at the terminals.

In R ¹ to R ³ of the above formulas (1) and (2), alkyl groups include C _1-14 alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, t-butyl, pentyl and hexyl. . Among C _1-14 alkyl groups, C _1-10 alkyl groups are preferred, and C _1-6 alkyl groups are more preferred.

Alkoxy groups include C _1-14 alkoxy groups such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, t-butoxy, pentyloxy and the like.

Alkenyl groups include C _2-14 alkenyl groups such as vinyl, allyl, butenyl, pentenyl and the like.

Cycloalkyl groups include C _5-14 cycloalkyl groups such as cyclopentyl, cyclohexyl, methylcyclohexyl, and the like. Cycloalkyloxy groups include C _5-14 cycloalkyloxy groups such as cyclopentyloxy and cyclohexyloxy. Cycloalkenyl groups include C _5-14 cycloalkenyl groups such as cyclopentenyl and cyclohexenyl.

Aryl groups include C _6-20 aryl groups such as phenyl, methylphenyl (tolyl), dimethylphenyl (xylyl), naphthyl, and the like. Among C _6-20 aryl groups, C _6-15 aryl groups are preferred, and C _6-12 aryl groups are more preferred.

Aryloxy groups include C _6-20 aryloxy groups such as phenoxy and naphthyloxy.

Aralkyl groups include C _6-20 aryl-C _1-4 alkyl groups such as benzyl, phenethyl, phenylpropyl, and the like.

Aralkyloxy groups include C _6-20 aryl-C _1-4 alkyloxy groups such as benzyloxy, phenethyloxy, phenylpropyloxy and the like.

Silyl groups include Si _1-10 silanyl groups such as silyl groups, disilanyl groups and trisilanyl groups. Among Si _1-10 silanyl groups, Si _1-6 silanyl groups are preferred.

Further, when R ¹ to R ³ are the above organic groups such as alkyl groups and aryl groups or silyl groups, at least one of the hydrogen atoms may be substituted with a substituent (or functional group). . Such substituents (or functional groups) may be, for example, groups similar to those described above, such as hydroxyl groups, alkyl groups, aryl groups, and alkoxy groups.

Of these, R ¹ to R ³ are generally alkyl groups and aryl groups. Among the alkyl groups, a C _1-4 alkyl group is preferred, and a methyl group is particularly preferred. Among the aryl groups, C _6-20 aryl groups are preferred, and phenyl groups are particularly preferred. Furthermore, R ¹ to R ³ are preferably a combination of a C _1-4 alkyl group and a C _6-20 aryl group, and particularly preferably a combination of a methyl group and a phenyl group.

When the polysilane has an acyclic structure such as a linear, branched, or network structure, the terminal may or may not be blocked. In the terminally uncapped polysilane, the terminal silicon atom usually has a hydrogen atom, a hydroxyl group, a halogen atom such as a chlorine atom, etc. in addition to the above-mentioned organic groups. Especially often they have. Furthermore, in polysilanes whose ends are not capped, the silicon atoms at the ends preferably contain an alkyl group or an aryl group as the organic group, since the effect of suppressing yellowing is great. Particular preference is given to including _1-3 alkyl groups and C _6-12 aryl groups such as phenyl groups.

Specific polysilanes include, for example, a linear polysilane having a structural unit represented by the above formula (1), a cyclic polysilane having a structural unit represented by the above formula (1), and a polysilane represented by the above formula (2). a branched polysilane having a structural unit represented by the above formula (2), a network polysilane having a structural unit represented by the above formula (2), and a polysilane having a combination of structural units represented by the above formulas (1) and (2) (branched chain-like or network-like polysilane) and the like. In these polysilanes, the structural units represented by formulas (1) and (2) may be used alone or in combination of two or more. The branched-chain or network-like polysilane may further contain a structural unit represented by the following formula (3).

Typical polysilanes include polydialkylsilanes, polyalkylarylsilanes, polydiarylsilanes, dialkylsilane-alkylarylsilane copolymers, which are chain (linear or branched) polysilane polysilanes, and cyclic polysilanes. polycyclic diarylsilane, which is a polysilane of

Examples of linear polydialkylsilanes include linear polydimethylsilane, polymethylpropylsilane, polymethylbutylsilane, polymethylpentylsilane, polydibutylsilane, polydihexylsilane, dimethylsilane-methylhexylsilane copolymer, and the like. and polysilanes containing a structural unit (R ³ is an alkyl group) represented by the above formula (2) as part of the linear polydialkylsilane.

Examples of the polyalkylarylsilane include linear polyalkylarylsilanes such as polymethylphenylsilane and methylphenylsilane-phenylhexylsilane copolymer, and a portion of the linear polyalkylarylsilane having the formula ( ² ) (wherein R3 is an alkyl group or an aryl group).

Examples of the polydiarylsilane include cyclic or linear polydiphenylsilane, and polysilane containing a structural unit (R ³ is an aryl group) represented by the above formula (2) as a part of the linear polydialkylsilane. etc.

Examples of the dialkylsilane-alkylarylsilane copolymer include dimethylsilane-methylphenylsilane copolymer, dimethylsilane-phenylhexylsilane copolymer, and dimethylsilane-methylnaphthylsilane copolymer.

These polysilanes can be used alone or in combination of two or more.

Among these, a chain or cyclic polysilane having a structural unit (1) in which R ¹ is an alkyl group or an aryl group and R ² is an aryl group is preferable, since it has a large effect of suppressing yellowing. More preferably, at least one selected from the group consisting of chain polyalkylarylsilanes such as polyC _1-6 alkylC _6-10 arylsilanes and cyclic polydiarylsilanes such as cyclic polydiC _6-10 arylsilanes, Most preferred are linear polyC _{1-3 alkylC 6-10} arylsilanes such as linear polymethylphenylsilane.

The weight average molecular weight of the polysilane can be selected, for example, from a range of about 400 to 50,000 in the measurement method by GPC (converted to polystyrene). 1200-5000, 1300-3000, and the most preferred range is 1500-2000. If the molecular weight of the polysilane is too small, the effect of suppressing the growth of spherulites in the polyolefin molded product is reduced. If the molecular weight of the polysilane is too small, the effect of suppressing yellowing may be reduced.

The average degree of polymerization of polysilane can be selected from the range of about 3 to 500 in terms of silicon atoms (that is, the average number of silicon atoms per molecule), for example, 7 to 100, preferably 8 to 50, more preferably 9 to 30, most preferably 10-20.

A preferable polysilane may be, for example, a chain polyalkylarylpolysilane represented by the following formula (A) or a cyclic polyarylsilane represented by the following formula (B).

(wherein R ⁴ represents an alkyl group, R ⁵ to R ⁷ represent aryl groups, and n1 and n2 are integers of 3-500).

The polysilane may be in a liquid state at room temperature of about 20° C., but is preferably in a solid state from the viewpoint of handleability.

Polysilane can be obtained by a conventional method. Conventional methods include dehalogen condensation polymerization of halosilanes using magnesium as a reducing agent (“magnesium reduction method”, WO98/29476, etc.), and dehalogen condensation polymerization of halosilanes in the presence of an alkali metal. ("Kipping method", J.Am.Chem.Soc., 110, 124 (1988), Macromolecules, 23, 3423 (1990), etc.), a method of dehalogen condensation polymerization of halosilanes by electrode reduction (J.Chem.Soc. , Chem. Commun., 1161 (1990), J. Chem. Soc., Chem. Commun. 897 (1992), etc.), a method of dehydrogenative condensation polymerization of hydrosilanes in the presence of a metal catalyst (JP-A-4-334551 JP-A-2003-120011), a method by anionic polymerization of disilene crosslinked with biphenyl or the like (Macromolecules, 23, 4494 (1990), etc.), a method by ring-opening polymerization of cyclic silanes, and the like.

The resin is a thermoplastic resin that is susceptible to heat history and is prone to yellowing. Examples of thermoplastic resins include, but are not limited to, polyethylene, polypropylene, poly-α-C _2-10 olefins such as polymethylpentene, and olefin-based resins such as cyclic polyolefins such as cyclopentadiene-based resins and norbornene-based resins; Vinyl, polyvinylidene chloride, vinyl resins such as vinyl acetate resins; aromatic vinyl resins such as polystyrene, acrylonitrile-styrene resin, styrene-methyl methacrylate resin, ABS resin; polymethyl methacrylate, (meth)acrylic acid - Homo or copolymer of (meth)acrylic monomers such as (meth)acrylic acid esters, acrylic resins such as methyl methacrylate-styrene copolymer; polycarbonate resins such as bisphenol A type polycarbonate; polyethylene terephthalate , poly-C2-10 alkylene- _{C6-10 arylates} or copolyesters such as polybutylene terephthalate, polycyclohexanedimethylene terephthalate, and polyethylene naphthalate; and polyester resins such as fluorene-containing polyesters, polyarylates, and liquid crystal polyesters; Polyacetal resins such as methylene; polyamide resins such as nylon 6, nylon 66, nylon 46, nylon 6T, nylon MXD; sulfone resins such as polysulfone and polyether sulfone; phenylene ether resins such as polyphenylene ether and modified polyphenylene ether thermoplastic elastomers such as styrene-based thermoplastic elastomers and olefin-based thermoplastic elastomers; and fluororesins such as polytetrafluoroethylene. These thermoplastic resins can be used alone or in combination of two or more.

Among these thermoplastic resins, at least one selected from the group consisting of olefin-based resins, polyester-based resins and polycarbonate-based resins is particularly preferred.

Olefin-based resins include low-density polyethylene, medium-density polyethylene, high-density polyethylene, polypropylene, and norbornene-based resins. These olefinic resins can be used alone or in combination of two or more. Among these, polyethylenes such as low-density polyethylene and medium-density polyethylene are preferred.

Polyester-based resins include aromatic polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. The aromatic polyester may be an aromatic polyester having a fluorene ring as an aromatic ring. These polyester resins can be used alone or in combination of two or more. Among these, polyalkylene arylates such as PET and fluorene-containing polyesters are preferred.

Bisphenol A type polycarbonate is preferable as the polycarbonate resin.

In the method of the present invention, for example, by subjecting these thermoplastic resins to extrusion molding or injection molding, yellowing of the thermoplastic resin can be suppressed even if it is subjected to heat history, and further, repeated heat history can be suppressed by recycling the thermoplastic resin. It is possible to suppress yellowing of thermoplastic resin even if it is subjected to severe heat history depending on manufacturing conditions and usage conditions.

According to the method of the present invention, yellowing of the resin can be suppressed even if the ratio of the polysilane to the thermoplastic resin is small. The weight ratio of the thermoplastic resin to the polysilane can be selected from the range of thermoplastic resin/polysilane=99.95/0.05 to 90/10, and the preferred range is 99.94/0 in the following steps. .06-95/5, 99.92/0.08-97/3, 99.9/0.1-98/2, 99.88/0.12-99/1, 99.85/0.15 ~99.5/0.5, 99.8/0.2 to 99.6/0.4, most preferably 99.75/0.25 to 99.65/0.35.

In the method of the present invention, in addition to the polysilane, a conventional stabilizer may be further blended. Commonly used stabilizers include heat stabilizers such as phenol compounds and phosphorus compounds, antioxidants such as amine compounds and phenol compounds, and light stabilizers such as benzotriazole compounds and benzophenone compounds. . However, it is also one of the important features of the present invention that the proportion of the stabilizer, which is a foreign substance for the thermoplastic resin, can be suppressed by blending the polysilane. Therefore, the proportion of the conventional stabilizer may be 50 parts by weight or less, for example 30 parts by weight or less, preferably 10 parts by weight or less, more preferably 5 parts by weight or less, with respect to 100 parts by weight of the polysilane, Most preferably it contains no conventional stabilizers. When a conventional stabilizer is included, the ratio of the conventional stabilizer may be 0.1-50 parts by weight per 100 parts by weight of polysilane.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited by these examples. Details of raw materials used in the following examples and comparative examples and methods for evaluating yellowing are shown below.

[raw materials used]
LLDPE: Low-density polyethylene, additive-free MDPE: SK-Global chemical Co., Ltd. "trade name YUCLAIR DX800"
PC: "Product name Novarex 7022PJ" manufactured by Mitsubishi Engineering-Plastics Co., Ltd.
Polymethylphenylsilane (molecular weight: 12,700): “Ogusol SI-10-10” manufactured by Osaka Gas Chemicals Co., Ltd., linear polymethylphenylsilane with unsealed ends, weight average molecular weight: 12,700
Polymethylphenylsilane (molecular weight 1,800): "Ogusol SI-10-20" manufactured by Osaka Gas Chemicals Co., Ltd., linear polymethylphenylsilane with unsealed ends, weight average molecular weight 1,800
Polydiphenylsilane (molecular weight 911): "Ogusol SI-30-10" manufactured by Osaka Gas Chemicals Co., Ltd., cyclic polydiphenylsilane, weight average molecular weight 911
Phenolic stabilizer: "Irganox 1010" manufactured by BASF Japan Co., Ltd.
Phosphorus-based stabilizer: "Irgafos 168" manufactured by BASF Japan Ltd.

[Yellowness YI]
The yellowness index YI of the pellets or three-stage plates obtained in Examples and Comparative Examples was measured according to ASTM E313-3.

Examples 1-4
Add 0.3 parts by weight of the polysilane shown in Table 1 to 99.7 parts by weight of the resin shown in Table 1, melt-knead at a temperature of 170 to 250 ° C. using an extruder, and granulate pellets. did. The granulation was repeated five times, the yellowness of the first pellet and the yellowness of the fifth pellet were measured, and the difference (ΔYI) between the two was determined.

Comparative Examples 1-2
Granulation was performed in the same manner as in Example 1 or 4 without adding polysilane, and ΔYI was determined.

Comparative Examples 3-4
Granulation was performed in the same manner as in Example 1 except that the stabilizers shown in Table 1 were used instead of polysilane, and ΔYI was determined.

Table 1 shows the results of Examples 1-4 and Comparative Examples 1-4.

As is clear from the results in Table 1, when the pellets of Examples mixed with polysilane were compared with the pellets of Comparative Examples 1 and 2, yellowing was suppressed even when subjected to heat history. Also, in Comparative Examples 3 and 4, in which a conventional stabilizer was blended, yellowing could not be suppressed.

Example 5
0.3 parts by weight of polymethylphenylsilane (molecular weight: 1800) is added to 99.7 parts by weight of polycarbonate, melt-kneaded at a temperature of 280° C. using an extruder, granulated, and then injection molded. A three-stage plate (1 mm thickness/2 mm thickness/3 mm thickness) was prepared from the pellets obtained using the machine, and the degree of yellowness was measured. Furthermore, the resulting three-stage plate was subjected to three conditions shown in Table 2 (622 hours under conditions of 85 ° C. and 85% RH, 1335 hours under conditions of 85 ° C. and 85% RH, 100 ° C. under atmospheric conditions 550 hours) and the yellowness was measured.

Comparative example 5
A three-stage plate was prepared in the same manner as in Example 5 without adding polysilane, and the yellowness index was measured.

The results of Example 5 and Comparative Example 5 are shown in Table 2.

As is clear from the results in Table 2, yellowing of the plate of Example 5 was suppressed more than the plate of Comparative Example 5.

The method of the present invention can be used as a method for suppressing yellowing of thermoplastic resins, and is particularly suitable as a method for suppressing yellowing of olefin resins, polyester resins, and polycarbonate resins.

Claims (4)

A method for suppressing yellowing of a resin, which comprises blending a thermoplastic resin with a chain polysilane having a structural unit represented by the following formula ( A ) and melt-kneading the mixture.

(wherein R ⁴ represents a C _1-6 alkyl group, R ⁵ represents a C _6-10 aryl group, and n1 is an integer of 3-500 ). 2. The method for suppressing yellowing of a resin according to claim 1, wherein the chain polysilane has a weight average molecular weight of 400 to 50,000. 3. The method for suppressing yellowing of a resin according to claim 1, wherein said thermoplastic resin is at least one selected from the group consisting of olefin resins, polyester resins and polycarbonate resins. The method for suppressing yellowing of a resin according to any one of claims 1 to 3 , wherein the thermoplastic resin and the linear polysilane are blended in a weight ratio of the former/latter = 99.95/0.05 to 90/10. .