JPH0665492A - Resin composition for block handle of toothbrush - Google Patents

Abstract

PURPOSE:To obtain the subject composition having excellent designing flexibility, chemical resistance, fatigue characteristics, fluidity, mold-releasability, notch sensitivity and mechanical properties such as rigidity by compounding particular components such as a specific aromatic polycarbonate resin and a specific polyester resin. CONSTITUTION:This resin composition having an elastic modulus of 20,000-27,000 kgf/cm<2> can be produced by compounding (A) 50-90wt.% of an aromatic polycarbonate resin having a viscosity-average molecular weight of 20,000-30,000 with (B) 50-10wt.% of a polyethylene terephthalate resin having an intrinsic viscosity of 0.6-1 and/or a polybutylene terephthalate resin having an intrinsic viscosity of 0.6-1.2 and compounding 100 pts. wt. of the obtained resin composition with (C) 1-15 pts.wt. of a thermoplastic polyester elastomer having a Shore hardness of 45-75, (D) 0.001-1 pt. wt. of a diphosphite compound of formula (R1 and R2 are H, alkyl, etc.) and (E) 0.001-2 pts. wt. of an ester of a 12-30C aliphatic saturated monobasic carboxylic acid and a <=30C saturated aliphatic alcohol.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a resin composition suitable for a handle of a toothbrush. More specifically, chemical resistance, fatigue characteristics,
The present invention relates to a resin composition suitable for a handle of a toothbrush, which has excellent rigidity, fluidity, releasability and notch resistance.

[0002]

2. Description of the Related Art Generally, a polypropylene resin is widely used as a material for a handle of a toothbrush because of its chemical resistance. However, since polypropylene resin has low rigidity, a considerable thickness is required, and there is a drawback that it is uncomfortable to use. In order to eliminate this drawback and enhance the usability of the toothbrush, use of a thermoplastic polyester resin such as a polyethylene terephthalate resin or a polybutylene terephthalate resin having high rigidity or an aromatic polycarbonate resin has been studied.

Thermoplastic polyester resins such as polyethylene terephthalate resin and polybutylene terephthalate resin have excellent rigidity and chemical resistance, but when fine scratches such as tooth contact scratches occur during tooth brushing, the fine scratches occur. There is a drawback that it is easy to break due to stress concentration of, that is, notch sensitivity is high. Furthermore, since the thermoplastic polyester resin has a high molding temperature and a low solidification temperature, that is, a glass transition temperature, the molding cycle becomes long and the cost becomes high. There is also a drawback. On the other hand, the aromatic polycarbonate resin is
Although it has excellent rigidity and fatigue characteristics, it has problems with chemical resistance, and toothpaste tends to cause microcracks.
It has the drawback that the bristles of the brush are easily pulled out when brushing teeth,
Further, it has a drawback that it has poor melt flowability and is difficult to be molded.

In order to take advantage of the preferred characteristics of each of the aromatic polycarbonate resin and the thermoplastic polyester resin,
We tried to mix the two, but there was a problem that the transesterification reaction between the resins, which adversely affects the chemical resistance, fatigue properties, and mechanical properties, progressed because it was necessary to raise the temperature to melt-knead them. In addition, there is also a problem that when a handle of a toothbrush is formed, particularly when a handle of a thin toothbrush having a good feeling of use is formed, it is easily affected by the stress at the time of mold release, and the fatigue characteristics deteriorate due to residual stress. Further, it is possible to improve notch sensitivity as compared with a polyethylene terephthalate resin or a polybutylene terephthalate resin by mixing a polycarbonate resin and a polyethylene terephthalate resin and / or a polybutylene terephthalate resin, but it is not sufficient and further improvement is necessary. is there. Therefore, there is a demand for a resin composition for a toothbrush handle, which has excellent design properties, chemical resistance, fatigue properties, mechanical properties such as rigidity, fluidity, release properties, and notch resistance.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide a resin composition for a handle of a toothbrush, which is excellent in designability, chemical resistance, fatigue characteristics, mechanical characteristics such as rigidity, fluidity, releasability and notch resistance. To provide things.

As a result of intensive studies to achieve the above object, the present inventors have found that a composition of a specific aromatic polycarbonate resin and a specific polyethylene terephthalate resin and / or polybutylene terephthalate resin has a specific thermoplasticity. The inventors have found that the target resin composition for a toothbrush handle can be obtained by adding small amounts of a polyester elastomer, a diphosphite compound, and an ester of an aliphatic carboxylic acid, respectively, and arrived at the present invention.

[0007]

According to the present invention, (A) 50 to 90% by weight of an aromatic polycarbonate resin having a viscosity average molecular weight of 20,000 to 30,000 and (B) an intrinsic viscosity of 0.
100 parts by weight of a resin composition consisting of 50 to 10% by weight of a polyethylene terephthalate resin having a viscosity of 6 to 1.0 and / or a polybutylene terephthalate resin having an intrinsic viscosity of 0.6 to 1.2, and (C) Shore D hardness. 1 to 15 parts by weight of a thermoplastic polyester elastomer having 45 to 75, (D) the following formula [1]

[0008]

[Chemical 2]

[Wherein R ₁ and R ₂ represent a hydrogen atom, an alkyl group, an arylalkyl group, an aryl group, an alkylaryl group, a 2- (4-oxyphenyl) propyl-substituted aryl group or a cycloalkyl group, and R ₁ And R ₂ may be the same or different. ] The diphosphite compound represented by 0.001 to 1 part by weight and (E) carbon number 1
Esters of 2 to 30 aliphatic saturated monovalent carboxylic acids and aliphatic saturated alcohols having 30 or less carbon atoms 0.001
Elasticity of 2 parts by weight is 20000-2700
The present invention relates to a resin composition for a toothbrush handle of 0 kgf / cm ² .

The polycarbonate resin used in the present invention has a viscosity average molecular weight of 20 derived from a dihydric phenol.
000-30000, preferably 22000-2700
It is an aromatic polycarbonate resin of 0 and is usually produced by reacting a dihydric phenol with a carbonate precursor by a solution method or a melting method. The dihydric phenol used here is 2,2-bis (4-hydroxyphenyl) propane [commonly called bisphenol A], but part or all of it may be replaced with another dihydric phenol. Other dihydric phenols include, for example, bis (4-hydroxyphenyl) methane and 2,2-bis (4-hydroxy-).
Examples include 3,5-dimethylphenyl) propane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, bis (4-hydroxyphenyl) sulfone and the like. Examples of the carbonate precursor include carbonyl halide, carbonyl ester, haloformate, and the like, and specifically, phosgene, diphenyl carbonate,
The dihaloformates of dihydric phenols and mixtures thereof. In producing the aromatic polycarbonate resin, an appropriate molecular weight modifier, branching agent, catalyst for accelerating the reaction and the like can be used. The molecular weight of such an aromatic polycarbonate resin is 20,000 to 300 in terms of viscosity average molecular weight.
00, preferably 22,000 to 27,000. If the viscosity average molecular weight is less than 20,000, the fatigue properties and chemical resistance will be poor, and if it exceeds 30,000, the fluidity will be reduced.

The polyethylene terephthalate resin used in the present invention is a polymer obtained by polycondensation reaction of terephthalic acid or its ester-forming derivative with ethylene glycol or its ester-forming derivative as a main raw material. It may be a copolymer in which mol% or less is replaced with another dicarboxylic acid, or 30 mol% or less of ethylene glycol is replaced with another aliphatic diol or alicyclic diol. Examples of the dicarboxylic acid used in such a copolymer include isophthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid and the like. Examples of the diol include polymethylene-α, ω-diols, neopentyl glycol, diethylene glycol and the like. The polyethylene terephthalate resin used in the present invention has an intrinsic viscosity of 0.6 to 1.0, preferably 0.65 to 0.95, measured at 25 ° C. with o-chlorophenol as a solvent. If the intrinsic viscosity is less than 0.6, notch sensitivity will be high, and if it exceeds 1.0, moldability will be deteriorated.

The polybutylene terephthalate resin used in the present invention is a polymer obtained by polycondensation reaction of terephthalic acid or its ester-forming derivative with tetramethylene glycol or its ester-forming derivative as a main raw material. A copolymer obtained by substituting 30 mol% or less of the above with another dicarboxylic acid, or substituting 30 mol% or less of tetramethylene glycol with another aliphatic diol or alicyclic diol may be used. Examples of the dicarboxylic acid used in such a copolymer include isophthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid and the like. Examples of the diol include polymethylene-α, ω
-Diols, neopentyl glycol, diethylene glycol and the like. The molecular weight of the polybutylene terephthalate resin used in the present invention is such that the intrinsic viscosity measured at 25 ° C. using o-chlorophenol as a solvent is from 0.6 to
1.2, preferably 0.65 to 1.0. If the intrinsic viscosity is less than 0.6, the notch sensitivity will be high, and if it exceeds 1.2, the moldability will be deteriorated.

The mixing ratio of the aromatic polycarbonate resin and the polyethylene terephthalate resin and / or the polybutylene terephthalate resin is 50 to 90% by weight for the former and 50 to 10% by weight for the latter. If the mixing ratio of the polyethylene terephthalate resin and / or polybutylene terephthalate resin is more than 50% by weight, notch sensitivity becomes high and fatigue resistance deteriorates, and if it is less than 10% by weight, chemical resistance and rigidity become insufficient. .

The thermoplastic polyester elastomer used in the present invention is a copolyester thermoplastic elastomer consisting essentially of repeating short chain ester units and long chain ester units linked through ester bonds. The short chain ester unit is usually 15 to 75% by weight of the copolyester and is represented by the following formula [2], and the long chain ester unit is usually 85 to 25% by weight of the copolyester and is represented by the following formula [3]. It is what is done.

[0015]

[Chemical 3]

[0016]

[Chemical 4]

[Wherein R is a divalent aromatic group obtained by removing a carboxyl group from an aromatic dicarboxylic acid having a molecular weight of less than 350, D is a divalent group obtained by removing a hydroxyl group from an organic diol having a molecular weight of less than 150, G Is an average molecular weight of 350 to 60
00 is a divalent group obtained by removing the terminal hydroxyl group from the long-chain glycol]

Such a thermoplastic polyester elastomer has a Shore D hardness of 45 to 75, and has a Shore D hardness of 50 to 7
0 is preferable. When the Shore D hardness is 45 or less, the chemical resistance is largely lowered, and when it is 75 or more, the notch sensitivity improving effect is insufficient. Further, those having a melting point of at least 125 ° C. are preferable. The blending ratio of the thermoplastic polyester elastomer is 1 to 15 parts by weight, preferably 3 to 12 parts by weight, based on 100 parts by weight of the composition comprising the aromatic polycarbonate resin and the polyethylene terephthalate resin and / or the polybutylene terephthalate resin. . If it is less than 1 part by weight, the effect of improving notch sensitivity is insufficient, and if it exceeds 15 parts by weight, the elastic modulus is lowered.

The diphosphite compound used in the present invention is represented by the above formula [1], and preferred specific examples thereof include the following compounds.

[0020]

[Chemical 5]

[0021]

[Chemical 6]

[0022]

[Chemical 7]

[0023]

[Chemical 8]

[0024]

[Chemical 9]

The diphosphite compound is added in an amount of 0.001 to 1 part by weight based on 100 parts by weight of the resin composition comprising the aromatic polycarbonate resin and the polyethylene terephthalate resin and / or the polybutylene terephthalate resin. If the amount added is less than 0.001 part by weight, the effect of preventing transesterification reaction during processing of the composition is insufficient, and if it exceeds 1 part by weight, bubbles are likely to be generated in the handle of the toothbrush obtained using the composition. In addition, the fatigue characteristics and chemical resistance will be adversely affected.

The ester of an aliphatic carboxylic acid used in the present invention comprises an aliphatic saturated monohydric carboxylic acid having 12 to 30 carbon atoms and an aliphatic saturated monohydric alcohol or saturated polyhydric alcohol having 30 or less carbon atoms. Is an ester or partial ester of. Many of such aliphatic esters are known as ester waxes contained in natural products such as plants, animals, insects and minerals, and for example, beeswax (a mixture containing myricyl palmitate as a main component), Examples include spalm acetyl (mixture containing cetyl palmitate as a main component), ethylene glycol ester of montanic acid, and the like.

The amount of the ester of the aliphatic saturated monovalent carboxylic acid and the aliphatic saturated alcohol added is 100 parts by weight of the resin composition comprising the aromatic polycarbonate resin and the polyethylene terephthalate resin and / or the polybutylene terephthalate resin. 0.001 to 2 parts by weight. If it is less than 0.001 part by weight, the releasing effect of the composition is insufficient, and if it exceeds 2 parts by weight, the fatigue properties are adversely affected.

The elastic modulus of the composition thus obtained is 200.
It should be between 0 and 27,000 kgf / cm ² . By having an elastic modulus in this range, the toothbrush with the best feeling of use can be obtained. That is, if it is less than 20000 kgf / cm ^2, it becomes too soft and becomes too flexible when it is used as a toothbrush with a thin neck, and if it exceeds 27,000 kgf / cm 2, the bending becomes small and the gums are easily damaged.

The resin composition for a toothbrush handle of the present invention contains a predetermined amount of the above aromatic polycarbonate resin, polyethylene terephthalate resin and / or polybutylene terephthalate resin, diphosphite compound and aliphatic ester, for example, tumbler, V-type. It can be manufactured by mixing with a mixer such as a blender, a Nauter mixer, a Banbury mixer, a kneading roll, and an extruder. In addition to the above components, other additives such as pigments, dyes and antibacterial agents may be added to the composition of the present invention within the range that does not impair the object of the present invention.

[0030]

EXAMPLES The present invention will be further described with reference to the following examples. In addition, the part in an Example is a weight part and evaluation was based on the following method. Chemical resistance: After applying a dentifrice [Aces manufactured by Sato Pharmaceutical Co., Ltd.] to a rod-shaped test piece having a length of 50 mm, a width of 5 mm and a thickness of 4 mm obtained by injection molding, a load of 2 kg and 4 Hz at 30 ° C. atmosphere. Under the conditions, a repeated bending fatigue test was performed using a servo pulser EHF-FD manufactured by Shimadzu Corporation, and the number of times until breakage was measured.
Those that did not break after 10,000 cycles were indicated by ◯, those that broke after 15,000 times and less than 25,000 cycles were marked by Δ, and those that broke after less than 15,000 cycles were marked by x.

Fatigue characteristics: length 50 mm obtained by injection molding,
A rod-shaped test piece with a width of 5 mm and a thickness of 4 mm is 2 kg in an atmosphere at 30 ° C.
Servo pulser made by Shimadzu Corporation under load and 4Hz
Repeated bending fatigue test was performed by EHF-FD, and the number of times until breakage was measured. ○ Those that did not break after 25,000 times were evaluated as ○, those that failed between 15,000 times and less than 25,000 times were evaluated as △, 1. What was broken after less than 50,000 times was shown by x.

Rigidity: The flexural modulus was measured according to ASTM D-790, and those of 20,000 to 27,000 kgf / cm ² are indicated by ◯, and the others are indicated by x.

Fluidity: injection molding machine [manufactured by Japan Steel Works, Ltd.]
J-120 SA] by a cylinder temperature of 260 ° C., a mold temperature of 70 ° C., an injection pressure of 800 kgf / cm ² by an Archimedes type spiral flow (3mm thick), measuring the flow length 2
0 cm or more is indicated by O, 15 cm or more and less than 20 cm is indicated by Δ, and less than 15 cm is indicated by X.

Mold release resistance: length 50 mm, width 5 mm, thickness 4 mm
The mold release resistance was measured by sticking a strain gauge to the projecting plate of the mold for making a test piece, and the measured value was shown.

Notch resistance: Impact strength was measured using a test piece having a thickness of ⅛ ″ according to ASTM D-256, and 10 kgf · cm.
/ Cm or more is indicated by ○, 4 kgf · cm / cm or more and less than 10 kgf · cm / cm is indicated by Δ, and less than 4 kgf · cm / cm is indicated by ×.

[0036]

Examples 1 to 6 and Comparative Examples 1 to 10 The components shown in Table 1 were mixed in the amounts shown in the table, and a cylinder temperature of 270 was obtained using a vent type extruder having a diameter of 30 mm [VSK-30 manufactured by Nakatani Co., Ltd.].
Pelleted at ° C. After drying the pellets at 120 ° C. for 5 hours, an injection molding machine [Japan Steel Works, Ltd. J-12
0 SA], cylinder temperature 270 ° C, mold temperature 70
Test pieces were prepared at 0 ° C., and the evaluation results are shown in Table 1.

The symbols showing the components shown in Table 1 are as follows. PC: Polycarbonate resin PC-1: Bisphenol A with viscosity average molecular weight 22,500
Type Polycarbonate Resin [L-122 manufactured by Teijin Chemicals Ltd.
5] PC-2: Bisphenol A having a viscosity average molecular weight of 25,000
Type Polycarbonate Resin [L-125 manufactured by Teijin Chemicals Ltd.
0] PC-3: Bisphenol A having a viscosity average molecular weight of 15,000
Type Polycarbonate resin PET: Polyethylene terephthalate resin PET-1: Polyethylene terephthalate resin with an intrinsic viscosity of 0.80 [TR-8580 manufactured by Teijin Ltd.] PET-2: Polyethylene terephthalate resin with an intrinsic viscosity of 0.71 [manufactured by Teijin Ltd.] TR-4550 BHK] PET-3: Polyethylene terephthalate resin with an intrinsic viscosity of 1.2 PBT: Polybutylene terephthalate resin PBT-1: Polybutylene terephthalate resin with an intrinsic viscosity of 0.87 [TRB-J] PBT- manufactured by Teijin Ltd. 2: Polybutylene terephthalate resin with an intrinsic viscosity of 0.70 [TRB-K manufactured by Teijin Ltd.] PBT-3: Polybutylene terephthalate resin with an intrinsic viscosity of 1.5 PSE: Thermoplastic polyester elastomer PSE-1: Shore D hardness 55 Thermoplastic polyester elastomer [Hytrel 555 manufactured by Toray DuPont Co., Ltd.
7] PSE-2: Thermoplastic polyester elastomer having a Shore D hardness of 40 [Hytrel 404 manufactured by Toray DuPont Co., Ltd.]
7] DP: diphosphite compound represented by the following formula

[0038]

[Chemical 10]

ES: ethylene glycol ester of montanic acid

[0040]

[Table 1]

[0041]

The resin composition for a toothbrush handle of the present invention comprises:
For example, it can be molded by any molding method such as injection molding, can be applied to a toothbrush with a thin neck portion, has excellent designability, fatigue characteristics and moldability, and can shorten the molding cycle.

Claims (1)

[Claims] 1. (A) The viscosity average molecular weight is 20,000 to 30.
50 to 90% by weight of an aromatic polycarbonate resin of 000 and (B) a polyethylene terephthalate resin having an intrinsic viscosity of 0.6 to 1.0 and / or an intrinsic viscosity of 0.6 to
Polybutylene terephthalate resin 50-1 which is 1.2
100 parts by weight of a resin composition consisting of 0% by weight, (C) 1 to 15 parts by weight of a thermoplastic polyester elastomer having a Shore D hardness of 45 to 75, (D) the following formula [1] [Here, R ₁ and R ₂ are a hydrogen atom, an alkyl group, an arylalkyl group, an aryl group, an alkylaryl group, 2-
(4-oxyphenyl) propyl-substituted aryl group or cycloalkyl group, and R ₁ and R ₂ may be the same or different. ] 0.001 to 1 part by weight of a diphosphite compound represented by the formula (E) 0.001 to an ester of an aliphatic saturated monovalent carboxylic acid having 12 to 30 carbon atoms and an aliphatic saturated alcohol having 30 or less carbon atoms The elastic modulus of 2 parts by weight is 20,000 to 27,000 kgf / cm ²
Resin composition for a toothbrush handle.