JP4954363B2 - Polyacetal resin composition excellent in dimensional stability and molded product thereof - Google Patents

Description

【０００７】
［但し、R₁、R₂、R₃、R₄は同一又は異なる置換基であり、水素原子、アルキル基（１〜５個の炭素を有し、０〜３個の水素がハロゲン原子で置換されたもの）を意味し、R₅はメチレン基、オキシメチレン基、アルキル基で置換されたメチレン基もしくはオキシメチレン基（この場合、ｐは０〜３の整数を表す）、或いは式-(CH₂)_q-OCH₂ 又は-(O-CH₂-CH₂)_q-OCH₂ で示される２価の基（この場合、ｐは１を表し、ｑは１〜４の整数を表す）を意味する。］
該コモノマーとしては、エチレンオキシド、エピクロルヒドリン、１，３−ジオキソラン、ジエチレングリコールホルマール、１，４−ブタンジオールホルマール、１，３−ジオキサン、プロピレンオキシド等が挙げられる。
【０００８】
次に、本発明で用いられる(B) 成分の炭素数が３以上の多価アルコールと脂肪酸とのフルエステル化合物とは、多価アルコールと、１価の飽和脂肪酸もしくは２塩基酸とのフルエステルであり、実用上好ましくは、炭素数８以上の飽和脂肪酸及び／又は多塩基酸とのフルエステルである。
【０００９】
炭素数が３以上の多価アルコールとしては、ジエチレングリコール、トリエチレングリコール、プロピレングリコール、ジプロピレングリコール、ブタンジオール、ペンタンジオール、ヘキサンジオール、グリセリン、ジグリセリン、トリグリセリン、トレイトール、エリスリトール、ペンタエリスリトール、アラビトール、リビトール、キシリトール、ソルバイト、ソルビタン、ソルビトール、マンニトール等が挙げられ、これらの１種以上が用いられる。
【００１０】
また、脂肪酸としては、カプリン酸、ラウリン酸、ミリスチン酸、パルミチン酸、ステアリン酸、アラキジン酸、ベヘン酸、モンタン酸、リグノセリン酸、ミリストレイン酸、パルミトレイン酸、オレイン酸、リノール酸、リノレン酸、リシノール酸、１２ヒドロキシステアリン酸、セバシン酸、ダイマー酸、及びかかる成分を含有してなる天然に存在する脂肪酸又はそれらの混合物等が挙げられる。
【００１１】
かかる(B) 成分のうち、摩擦・摩耗特性、寸法安定性の点で、特に好ましく用いられるものは、グリセリントリステアレート、グリセリントリ１２ヒドロキシステアレート、グリセリントリベヘネート、グリセリントリアジペート、グリセリントリフタレート、ペンタエリスリトールテトラステアレート、及びそれらの誘導体であり、本発明においてはこれらのフルエステル化合物から選ばれた１種又は２種以上が用いられる。
【００１２】
(B) 成分の配合量は、(A) ポリアセタール樹脂100 重量部に対して、0.05〜10重量部、好ましくは0.5 〜５重量部である。0.05重量部未満では摩擦・摩耗特性が不充分であり、10重量部を越えると成形性の悪化を招き好ましくない。
【００１３】
本発明の樹脂組成物には、更に公知の各種添加剤を配合し得る。例えば、各種の着色剤、離型剤、核剤、帯電防止剤、その他の界面活性剤、各種ポリマー等である。また、本発明の目的とする成形品の性能を大幅に低下させないような範囲であるならば、公知の無機、有機、及び金属等の繊維状、板状、粉粒状等の充填剤を１種又は２種以上複合させて配合することも可能である。このような充填剤の例としては、ガラス繊維、ガラスビーズ、タルク、マイカ、ウォラストナイト、炭素繊維等が挙げられるが、何らこれらに限定されるものではない。
【００１４】
本発明の組成物の調製法は特に制限がなく、従来の樹脂組成物調製法として一般に用いられる公知の方法により容易に調製される。例えば、ｉ）各成分を混合した後、一軸又は二軸の押出機により練混み押出ししてペレットを調製し、しかる後に成形する方法、ii）一旦組成の異なるペレット（マスターバッチ）を調製し、そのペレットを所定量混合（稀釈）して成形に供し、成形後に目的組成の成形品を得る方法、 iii）成形機に各成分の１又は２種以上を直接仕込む方法等、何れも使用できる。また、樹脂成分の一部を細かい粉体として、これ以外の成分と混合し添加することは、これらの成分の均一配合を行う上で好ましい方法である。
【００１５】
また本発明の樹脂組成物は、押出成形、射出成形、圧縮成形、真空成形、吹込成形、発泡成形等の何れによっても成形可能である。このようにして得られる本発明の成形品は、優れた摩擦・摩耗性を有し、且つ寸法安定性に優れているので、このような性能が要求される用途、特に歯車、レバー、カム、スライダー、軸受け等の摺動部品に特に好適に用いられる。
【００１６】
【実施例】
以下、実施例により本発明を更に具体的に説明するが、本発明はこれらに限定されるものではない。実施例及び比較例の各特性値は、次のようにして求めた。
〔摩擦係数〕
鈴木式摩擦摩耗試験機を用い、初期の摩擦係数と、加圧0.75kg/cm²、線速度180mm/sec 、接触面積2.0cm²、相手材としてポリアセタール樹脂材料（ポリプラスチックス（株）製、商品名Ｍ９０−４４）を用い、24時間摺動させた後の動摩擦係数を測定した。
〔寸法変化量〕
ＡＳＴＭ引張試験片を成形し、試験片を温度23℃、湿度50％の空調室に24時間放置した後に、試験片の寸法（縦方向の長さ）を正確に測定した。その後、以下の２条件にて試験片を処理し、再び上記空調室に24時間放置した後に、寸法を測定した。初期の寸法と処理後の寸法の差を寸法変化量とした。
条件▲１▼；70℃×４時間
条件▲２▼；60℃×３時間→−20℃×３時間を12サイクル
実施例１〜８、比較例１〜７
(A) ポリアセタール樹脂（ポリプラスチックス（株）製、商品名ジュラコン）に、表１に示す(B) フルエステル化合物を、表１に示す割合で添加し、混合した後、二軸押出機により溶融混練し、ペレット状の組成物を調製した。次いで、該ペレットを用いて上記の評価を行った。結果を表１に示す。
【００１７】
比較のため、(B) フルエステル化合物を配合しないもの、モノエステル化合物等のフルエステル化合物でないものを用いた場合について、同様に評価を行った。結果を表２に示す。
【００１８】
尚、使用したエステル化合物は以下のものである。
b-1 ：グリセリントリステアレート
b-2 ：グリセリントリ１２ヒドロキシステアレート
b-3 ：グリセリントリベヘネート
b-4 ：グリセリントリアジペート
b-5 ：ペンタエリスリトールテトラステアレート
b'-1：グリセリンモノステアレート
b'-2：グリセリンジステアレート
b'-3：グリセリンモノ１２ヒドロキシステアレート
b'-4：グリセリンモノベヘネート
b'-5：グリセリンモノアジペート
b'-6：ペンタエリスリトールトリステアレート
【００１９】
【表１】

【００２０】
【表２】

【００２１】
【発明の効果】
以上の説明及び実施例から明らかなように、多価アルコールと脂肪酸とのフルエステル化合物が添加されたポリアセタール樹脂組成物は、摺動特性に優れ、且つ環境温度による寸法変化が少なく、結晶状態の安定のために長時間アニールしなくとも、摺動部材として好適に使用することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyacetal resin composition having excellent friction and wear properties and improved dimensional stability of a molded product.
[0002]
[Prior art and problems to be solved by the invention]
Polyacetal resins have balanced mechanical properties and have excellent slidability as resins, and thus are widely used in the fields of automobiles, electrical / electronic parts, office equipment, building materials and the like. However, as the use expands and the use at high speed and high load increases, the demand for such sliding parts tends to become more sophisticated. For example, regarding mechanical parts such as gears, after-shrinkage occurs due to an increase in the environmental temperature inside the actual machine mechanism, and if the gears are engaged, there is a problem of meshing misalignment, resulting in problems such as poor torque transmission. In order to solve these problems, it is common practice to increase the dimensional accuracy by annealing for a long time after molding at a temperature below the melting point of the resin and stabilizing the crystalline state of the polyacetal. Not only is the cost high, but abrupt crystal shrinkage immediately after molding causes defects in the molded product, which also decreases durability. Further, since this defect is further increased by repeated heating and cooling, a resin material that maintains excellent dimensional stability against temperature changes has been desired.
[0003]
[Means for Solving the Problems]
As a result of intensive studies to provide a polyacetal resin composition capable of meeting such requirements, the present inventors have excellent friction and wear properties and are dimensionally stable by blending a specific ester compound with the polyacetal resin. The present inventors have found that a polyacetal resin composition having improved properties can be obtained, and have reached the present invention.
[0004]
That is, the present invention provides (A) 100 parts by weight of a polyacetal resin and (B) dimensional stability obtained by blending 0.05 to 10 parts by weight of a full ester compound of a polyhydric alcohol having 3 or more carbon atoms and a fatty acid. The present invention relates to a polyacetal resin composition excellent in the above.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below. The polyacetal resin (A) used in the present invention is a polymer compound having an oxymethylene group (—CH ₂ O—) as a main structural unit, and a polyacetal copolymer containing a small amount of other structural units in addition to the oxymethylene group ( For example, “Duracon” manufactured by Polyplastics Co., Ltd. is preferable, and a polyacetal copolymer obtained by copolymerizing 1 to 30% by weight of a comonomer component is particularly preferable because it can maintain excellent thermal stability and mechanical strength. In addition, the polyacetal copolymer may have a molecule having a branched or crosslinked structure as well as a linear shape. The viscosity of the polyacetal resin is not particularly limited as long as molding is possible, but the melt index (ASTM D-1238-89E) is preferably 5 to 100 g / 10 min. Although the comonomer component used for manufacture of a polyacetal copolymer is not specifically limited, Generally the compound shown by the following general formula is used.
[0006]
[Chemical 1]

[0007]
[However, R ₁ , R ₂ , R ₃ , R ₄ are the same or different substituents, and are a hydrogen atom or an alkyl group (having 1 to 5 carbons, and 0 to 3 hydrogens are substituted with halogen atoms. R ₅ represents a methylene group, an oxymethylene group, a methylene group substituted with an alkyl group or an oxymethylene group (in this case, p represents an integer of 0 to 3), or a formula — (CH _{2) q} -OCH ₂ or _{- (O-CH 2 -CH 2} ) 2 divalent group represented by _q -OCH ₂ (in this case, p is represents 1, q is meant represents) an integer of 1 to 4 To do. ]
Examples of the comonomer include ethylene oxide, epichlorohydrin, 1,3-dioxolane, diethylene glycol formal, 1,4-butanediol formal, 1,3-dioxane, propylene oxide, and the like.
[0008]
Next, the full ester compound of a polyhydric alcohol having 3 or more carbon atoms and a fatty acid as the component (B) used in the present invention is a full ester of a polyhydric alcohol and a monovalent saturated fatty acid or dibasic acid. Practically preferred are full esters with saturated fatty acids having 8 or more carbon atoms and / or polybasic acids.
[0009]
Examples of the polyhydric alcohol having 3 or more carbon atoms include diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, hexanediol, glycerin, diglycerin, triglycerin, threitol, erythritol, pentaerythritol, Examples thereof include arabitol, ribitol, xylitol, sorbite, sorbitan, sorbitol, mannitol and the like, and one or more of these are used.
[0010]
As fatty acids, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, montanic acid, lignoceric acid, myristoleic acid, palmitoleic acid, oleic acid, linoleic acid, linolenic acid, ricinol Examples include acids, 12 hydroxystearic acid, sebacic acid, dimer acid, naturally occurring fatty acids containing such components, or mixtures thereof.
[0011]
Among these components (B), those particularly preferably used in terms of friction / wear characteristics and dimensional stability are glycerin tristearate, glycerin tri-12 hydroxystearate, glycerin tribehenate, glycerin triadipate, glycerin. These are triphthalate, pentaerythritol tetrastearate, and derivatives thereof. In the present invention, one or more selected from these full ester compounds are used.
[0012]
The amount of component (B) is 0.05 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of (A) polyacetal resin. If it is less than 0.05 part by weight, the friction and wear characteristics are insufficient, and if it exceeds 10 parts by weight, the moldability is deteriorated, which is not preferable.
[0013]
The resin composition of the present invention may further contain various known additives. For example, various colorants, release agents, nucleating agents, antistatic agents, other surfactants, various polymers, and the like. Moreover, if it is the range which does not reduce the performance of the molded article made into the objective of this invention significantly, 1 type of well-known fillers, such as fiber, plate shape, and granular form, such as inorganic, organic, and metal, are included. Or it is also possible to mix | blend and mix 2 or more types. Examples of such a filler include, but are not limited to, glass fiber, glass bead, talc, mica, wollastonite, carbon fiber and the like.
[0014]
The method for preparing the composition of the present invention is not particularly limited, and it can be easily prepared by a known method generally used as a conventional method for preparing a resin composition. For example, i) a method of mixing each component, then kneading and extruding with a single screw or twin screw extruder to prepare pellets, and thereafter forming a pellet; ii) preparing pellets (master batches) having different compositions once; Any method can be used, such as a method in which a predetermined amount of the pellets are mixed (diluted) and subjected to molding to obtain a molded product of the desired composition after molding, or iii) one or more of each component is directly charged into a molding machine. Moreover, mixing a part of the resin component as a fine powder and adding it with other components is a preferable method for uniformly blending these components.
[0015]
The resin composition of the present invention can be molded by any of extrusion molding, injection molding, compression molding, vacuum molding, blow molding, foam molding, and the like. The molded product of the present invention thus obtained has excellent friction and wear properties and is excellent in dimensional stability. Therefore, it is used for applications requiring such performance, particularly gears, levers, cams, It is particularly preferably used for sliding parts such as sliders and bearings.
[0016]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. Each characteristic value of an Example and a comparative example was calculated | required as follows.
〔Coefficient of friction〕
Using a Suzuki friction and wear tester, the initial friction coefficient, pressurization 0.75kg / cm ² , linear velocity 180mm / sec, contact area 2.0cm ² , polyacetal resin material (manufactured by Polyplastics Co., Ltd., Using a product name M90-44), the coefficient of dynamic friction after sliding for 24 hours was measured.
[Dimensional change]
An ASTM tensile test piece was formed, and the test piece was allowed to stand in an air-conditioned room at a temperature of 23 ° C. and a humidity of 50% for 24 hours, and then the dimension (length in the longitudinal direction) of the test piece was accurately measured. Thereafter, the test piece was treated under the following two conditions, and again left in the air-conditioned room for 24 hours, and then the dimensions were measured. The difference between the initial dimension and the dimension after processing was defined as the dimensional change.
Condition (1): 70 ° C. × 4 hours Condition (2); 60 ° C. × 3 hours → −20 ° C. × 3 hours 12 cycles Examples 1-8, Comparative Examples 1-7
(A) Polyacetal resin (manufactured by Polyplastics Co., Ltd., trade name Duracon), (B) full ester compound shown in Table 1 was added at a ratio shown in Table 1, mixed, and then mixed with a twin screw extruder. The mixture was melt-kneaded to prepare a pellet-shaped composition. Next, the above evaluation was performed using the pellets. The results are shown in Table 1.
[0017]
For comparison, the same evaluation was performed for the case where (B) a non-full ester compound or a non-full ester compound such as a monoester compound was used. The results are shown in Table 2.
[0018]
The ester compounds used are as follows.
b-1 glycerin tristearate
b-2: glycerin tri-12 hydroxystearate
b-3: Glycerin tribehenate
b-4: Glycerin triadipate
b-5: Pentaerythritol tetrastearate
b'-1: Glycerol monostearate
b'-2: Glycerol distearate
b'-3: Glycerin mono-12 hydroxystearate
b'-4: Glycerin monobehenate
b'-5: Glycerol monoadipate
b'-6: Pentaerythritol tristearate
[Table 1]

[0020]
[Table 2]

[0021]
【Effect of the invention】
As is clear from the above description and examples, the polyacetal resin composition to which a full ester compound of a polyhydric alcohol and a fatty acid is added is excellent in sliding characteristics, has little dimensional change due to environmental temperature, and has a crystalline state. Even if it does not anneal for a long time for stability, it can be suitably used as a sliding member.

Claims (2)

Against 100 parts by weight of the polyacetal resin, (B) by blending a full ester compound 0.05 to 10 parts by weight of glycerin and the number 8 or more saturated fatty acids of carbon, Po Li acetal resin composition resin component is only polyacetal resin Sliding parts selected from gears, levers, cams, sliders and bearings formed by molding objects . (B) A sliding part selected from gears, levers, cams, sliders and bearings formed by molding the polyacetal resin composition according to claim 1, wherein the full ester compound is glycerin tristearate and / or a derivative thereof.