JP4655499B2 - Thermoplastic polyurethane elastomer - Google Patents

Description

  The present invention relates to a thermoplastic polyurethane elastomer. More specifically, the present invention relates to a thermoplastic polyurethane elastomer that is effectively used as a molding material for a cushioning material with little temperature dependency.

  Conventional polymer cushioning materials used for impact absorption include natural rubber, styrene rubber, butadiene rubber, isoprene rubber, butyl rubber, ethylene-vinyl acetate copolymer, epoxy resin, vinyl chloride resin or these. In addition, a composition obtained by alloying the above and a composition in which a filler such as graphite, calcium carbonate, iron oxide, carbon black, and mica is dispersed is known.

  However, the buffering properties of these polymer-based materials greatly depend on temperature, and their properties are limited to a narrow temperature range. Moreover, when forming into the shape of a rubber member using these compositions, the problem that a use is limited from the problem that a moldability is bad and a shape cannot be hold | maintained is also seen. Furthermore, in such elastomer composites, plasticizers and additives are often used to improve vibration damping and buffering properties, and as a result, they are used as non-volatile residues. It tends to deposit on the surface, which is also a factor that narrows the application range.

On the other hand, thermoplastic polyurethane elastomers are generally excellent in molding processability, have few non-volatile residues, and have been used as multi-purpose buffer materials. There is a characteristic of high nature.
Issued by the Industrial Research Council, “Encyclopedia of Plastics and Functional Polymers”, page 426 (2004)

  For example, in a hard disk drive (HDD), when the buffering capacity of the stopper is small (deceleration is large), the parallel movement energy of the arm is easily converted into vibration energy in the vertical direction, and there is a high possibility of damaging the hard disk. Become. On the other hand, even if the material has high cushioning properties, if the amount of displacement increases at high temperatures, the range of movement of the head unit that reads information from the hard disk is expanded, and there is a risk of damage due to contact with other components.

  An object of the present invention is to provide a thermoplastic polyurethane elastomer having a high shock-absorbing property and a stable load displacement amount in a wide temperature range from a low temperature to a high temperature and having excellent moldability.

An object of the present invention is to provide 5 to 40 mol of a prepolymer obtained by reacting 10 to 40 mol% of polytetramethylene glycol having a number average molecular weight Mn of 500 to 3000 and 45 to 55 mol% of o-tolidine diisocyanate. % Of the JIS A hardness obtained by reacting with a diol having an aromatic ring of 70 to 98, and the amount of deflection of the load in the temperature range of 0 to 80 ° C. (displacement at a load of 1 N) The difference is 10% or less, and is achieved by a thermoplastic polyurethane elastomer used as a molding material for hard disk drive stoppers.

The thermoplastic polyurethane elastomer according to the present invention itself has excellent buffering properties, the JIS A hardness is 70 to 98, and the temperature dependence of load deflection (displacement under a constant load) is also 0 to 80 ° C. The difference in temperature range is as small as 10% or less, so it is very useful as a molding material for HDD stoppers used in a wide temperature range. Moreover, the material fluidity at the time of molding is good, and a product having a complicated shape can be easily injection molded.

As the polytetramethylene glycol constituting the polyether polyol, those having a number average molecular weight Mn of 500 to 3000, preferably 850 to 2000, particularly preferably about 1000 to 1500 are used. If the average molecular weight is smaller than this, the rigidity at high temperature will be poor, and the shape stability due to heating and softening will be lacking. On the other hand, if it is larger than this, the flexibility at low temperature will be reduced. Become scarce.

  These polytetramethylene glycols are used in a proportion of 10 to 40 mol%, preferably 13 to 37 mol%, based on 45 to 55 mol%, preferably 50 to 55 mol% of aromatic diisocyanate in the total number of moles of reaction raw materials. It is done. If the ratio is more than this, the resulting thermoplastic polyurethane elastomer has poor thermal stability, whereas if it is used at a ratio less than this, the flexibility of the resulting thermoplastic polyurethane elastomer at low temperatures tends to be impaired.

  Aromatic diisocyanates used to react with polytetramethylene glycol to form a prepolymer include, for example, o-tolidine diisocyanate (3,3'-dimethyldiphenyl-4,4'-diisocyanate), p-phenylene diisocyanate, Examples include tolylene diisocyanate, toluene diisocyanate, xylylene diisocyanate, and naphthalene diisocyanate. Preferably, o-tolidine diisocyanate is used because of the non-temperature dependence of the deflection amount under load. In contrast, in the case of methylene bis (4-phenyl isocyanate) in which the aromatic group is bonded to the alkylene group even though it is an aromatic diisocyanate, the TMA displacement amount is large as shown in the results of Comparative Example 1 described later. This is presumably because the rigidity at high temperature is lost due to the methylene bond bonded to the aromatic group.

Examples of the diol having an aromatic ring used as a chain extender include aromatics such as 1,4-bis (2-hydroxyethoxy) benzene, bis (2-hydroxyethyl) terephthalate, and p-hydroxyphenethyl alcohol. A diol having a ring, preferably 1,4-bis (2-hydroxyethoxy) benzene, is used. When a diol having an aromatic ring is used as a chain extender, combined with the use of an aromatic diisocyanate, it results in an increase in the aromatic ring concentration of the hard segment, which is excellent in the low temperature region together with the polyether soft segment. A thermoplastic polyurethane elastomer that maintains flexibility and has shape stability in a high temperature region can be obtained.

The diol having an aromatic ring as a chain extender is used in a proportion of 5 to 40 mol%, preferably 12 to 35 mol% in the total number of moles of reaction raw materials. If the proportion of the chain extender diol is less than this, the proportion of the hard segment is small and the rigidity at high temperature is poor, while if it is used in a proportion higher than this, the proportion of the hard segment is too large, That is, the proportion of the soft segment becomes too small, and the flexibility at low temperatures becomes poor. The ratio of the number of moles of NCO groups in the aromatic diisocyanate to the total OH groups in the polytetramethylene glycol and the chain extender diol (NCO / OH) is 0.9 to 1.2, preferably 1.0 to 1.1.

  As a method for producing a thermoplastic polyurethane elastomer, a prepolymer method in which polytetramethylene glycol and an aromatic diisocyanate are reacted to obtain a prepolymer and then reacted with a chain extender is preferably used. It can also be synthesized by a one-shot method in which an aromatic diisocyanate is added to and reacted with a mixture with a chain extender diol. In these reactions, a catalyst such as tertiary amines such as 1,4-diazabicyclo [2.2.2] octane can be used as necessary.

To the thermoplastic polyurethane elastomer obtained as a result of the reaction, if necessary, a release agent, a colorant, a lubricant, a plasticizer, a coupling agent, a heat stabilizer, a flame retardant, and the like are added, and then a well-known molding method, For example, it is molded into an HDD stopper shape by injection molding or extrusion. Of these various molding methods, the injection molding method is preferable from the viewpoint of workability and productivity.

  Next, the present invention will be described with reference to examples.

Example 1
Polytetramethylene glycol (Hodogaya Chemicals PTG-850SN; Mn850) 37 mol% and o-tolidine diisocyanate 51 mol% were reacted to obtain a prepolymer. To this prepolymer, 12 mol% of 1,4-bis (2-hydroxyethoxy) benzene (Suntechnochemical product) was added and a chain extender reaction was performed to obtain a thermoplastic polyurethane elastomer.

Example 2
In Example 1, 32 mol% of Mn1400 (Hodogaya Chemical Product PTG-1400SN) was used as polytetramethylene glycol, and the amount of 1,4-bis (2-hydroxyethoxy) benzene was changed to 17 mol%.

Example 3
In Example 2, the amount of polytetramethylene glycol was changed to 14 mol%, and the amount of 1,4-bis (2-hydroxyethoxy) benzene was changed to 35 mol%.

Example 4
In Example 1, 28 mol% of Mn2000 (Hodogaya Chemical Product PTG-2000SN) was used as polytetramethylene glycol, and the amount of 1,4-bis (2-hydroxyethoxy) benzene was changed to 21 mol%.

Comparative Example 1
In Example 2, the same mole% of methylene bis (4-phenyl isocyanate) was used as the diisocyanate, the amount of polytetramethylene glycol was 30 mole%, and the amount of 1,4-bis (2-hydroxyethoxy) benzene was 19 mole%. Respectively changed.

Comparative Example 2
In Example 2, 1,4-butanediol was used in the same number of moles as a chain extender.

Comparative Example 3
In Example 2, 19 mol% of polycaprolactone glycol (Dainippon Ink Chemical Co., Ltd. product Polylite ODX-705R; Mn2000) was used as the polyol, and the amount of 1,4-bis (2-hydroxyethoxy) benzene was 30 mol%. changed.

For the thermoplastic polyurethane elastomers of the above Examples and Comparative Examples, the following items were measured.
Normal properties: JIS K6253 compliant (hardness), JIS K6251 compliant (100% modulus, tensile strength, elongation
B)
TMA displacement: A thermoplastic polyurethane elastomer with a cylinder temperature of 180 to 230 ° C and a mold temperature of 30 to 50 ° C was used to produce a 120 x 35 x 2 mm sheet material. Using a TA instrument 2940 thermomechanical analyzer, force was applied to the 0.89 mm diameter probe for penetration measurement at an initial pressure of 0.01 N to 1.0 N / min and finally a load of 1.00 N Measured at 0 ℃, 40 ℃, and 80 ℃.

The results obtained are shown in the following table.
table
Example Comparative Example
Measurement item 1 2 3 4 1 2 3
Normal physical properties Hardness (JIS A) 84 79 98 82 80 82 82
100% modulus (MPa) 5.51 4.51 22.3 5.52 4.95 5.31 5.38
Tensile strength (MPa) 32.6 31.2 44.7 36.0 38.5 28.2 44.6
Elongation (%) 680 670 520 690 720 800 580
TMA displacement (at 1N load)
0 ° C (μm) 58.9 66.8 14.7 61.8 74.4 69.4 51.2
40 ° C (μm) 59.0 66.0 15.6 62.4 77.5 73.0 58.4
80 ° C (μm) 60.5 69.8 16.0 66.2 87.9 92.6 70.7

The thermoplastic polyurethane elastomer according to the present invention exhibits stable buffer properties and load displacement over a wide temperature range of about 0 to 80 ° C., and therefore can be effectively used as a molding material for HDD stoppers.

Claims (1)

Diol having an aromatic ring of 5 to 40 mol% to a prepolymer obtained by reacting 10 to 40 mol% of polytetramethylene glycol having a number average molecular weight Mn of 500 to 3000 and 45 to 55 mol% of o-tolidine diisocyanate The JIS A hardness obtained by reacting the chain is 70 to 98, and the difference in load deflection (displacement at 1N load) in the temperature range of 0 to 80 ° C is 10% or less. A thermoplastic polyurethane elastomer used as a molding material for hard disk drive stoppers.