Patent Description:
Since thermoplastic polyamides having both hard segments and soft segments and phase-separated structures formed in respective segments are easily melt processed and highly flexible, they have been used for tubes, hoses, shoes, sealing materials, etc. The thermoplastic polyamides often have hard segments constructed of crystalline polyamide such as polyamide <NUM>, polyamide <NUM>, or polyamide <NUM>, and soft segments constructed of a block copolymer formed of polyether or the like, and the bond between the hard segment and the soft segment is often an ester bond.

However, the thermoplastic polyamide resin including the above structures has a problem of having a lower melting point and a lower thermal resistance than the thermoplastic polyester having hard segments and soft segments.

Polymerization at an elevated temperature is required for manufacture of a polyamide having a high melting point. However, at a high polymerization temperature, soft segments are decomposed and shortened in the length by water generated in condensation reaction, amino groups contained in raw material monomers, and amino groups generated in hydrolysis of the polyamide, which results in a problem of lowering a molecular weight of the obtained polyamide and exhibiting insufficient performance.

As thermoplastic polyamides having a high thermal resistance and having hard segments and soft segments, for example, Patent Literature <NUM> discloses polyamides including a unit formed from an aliphatic polyamide-forming monomer, a unit formed from a polycarbonate diol, and a unit formed from a dicarboxylic acid.

Further, Patent Literature <NUM> discloses polyamides, Patent Literature <NUM> discloses a polyether polyamide composition, Patent Literature <NUM> discloses a polyamide containing monomer units of <NUM>,<NUM>-butylene diamine, Patent Literature <NUM> discloses copolyamides with alternating repeat units, Patent Literature <NUM> discloses a copolyamide, Patent Literature <NUM> discloses a homogeneous, flexible block copolyetheramide having oxyalkylene units and Patent Literature <NUM> discloses a homogenous hexamethylenediamine/adipic acid/dimer acid copolyamide preparation.

However, the thermoplastic polyamides disclosed in Patent Literature <NUM> have higher melting points than conventional polyamides but of at most <NUM> and thus insufficient thermal resistance.

An object of the present invention is to solve the above problems and provide a polyamide forming a phase-separated structure composed of soft segments and hard segments, which is considered to be preferred as a highly flexible morphology, without including a polyether or polyester component that is more decomposable during polymerization, and having an excellent flexibility and a high melting point.

The present inventors have found, as a result of diligent efforts to solve the above problems, that a polyamide including <NUM> to <NUM>% by mass in total of a unit formed from an aliphatic dicarboxylic acid having <NUM> or more carbon atoms and/or a unit formed from an aliphatic diamine having <NUM> or more carbon atoms can achieve the object, and thus have completed the present invention.

More specifically, the invention is as set forth in the appended set of claims.

According to the present invention it is possible to provide a polyamide excellent in flexibility and having a high melting point since it includes a specific amount of a unit formed from an aliphatic dicarboxylic acid having <NUM> or more carbon atoms and/or a unit formed from an aliphatic diamine having <NUM> or more carbon atoms, without including a polyether or polyester component which is apt to decompose during polymerization.

The polyamide of the present invention needs to include a unit formed from an aliphatic dicarboxylic acid (A1) having <NUM> or more carbon atoms and/or a unit formed from an aliphatic diamine (B1) having <NUM> or more carbon atoms. In the polyamide of the present invention, the unit formed from (A1) and/or the unit formed from (B1) form soft segments.

In the polyamide of the present invention, a total content of the unit formed from (A1) and the unit formed from (B1) needs to be <NUM> to <NUM>% by mass, and it is preferably <NUM> to <NUM>% by mass, more preferably <NUM> to <NUM>% by mass, and still more preferably <NUM> to <NUM>% by mass. If the total content in the polyamide of the present invention is less than <NUM>% by mass, the flexibility is lowered, while if the total content is more than <NUM>% by mass, the thermal resistance is lowered.

From the viewpoints of flexibility and elongation of the polyamide of the present invention, it preferably simultaneously includes the unit formed from the aliphatic dicarboxylic acid (A1) having <NUM> or more carbon atoms and the unit formed from the aliphatic diamine (B1) having <NUM> or more carbon atoms, and the mass ratio (unit formed from (A1)/unit formed from (B1)) is preferably <NUM>/<NUM> to <NUM>/<NUM>, more preferably <NUM>/<NUM> to <NUM>/<NUM>, and still more preferably <NUM>/<NUM> to <NUM>/<NUM>.

Incidentally, it is preferred to include the unit formed from the aliphatic diamine (B1) having <NUM> or more carbon atoms without (A1) than to include the unit formed from the aliphatic dicarboxylic acid (A1) having <NUM> or more carbon atoms without (B1), from the viewpoints of flexibility and thermal resistance.

The aliphatic dicarboxylic acid (A1) having <NUM> or more carbon atoms is preferably formed from hydrocarbon only except for the carboxyl groups and includes, for example, hexadecanedicarboxylic acid (<NUM> carbon atoms), octadecanedicarboxylic acid (<NUM> carbon atoms), and dimer acid (<NUM> carbon atoms).

Among these, (A1) is more preferably an aliphatic dicarboxylic acid having <NUM> or more carbon atoms, and still more preferably dimer acid because such a type of (A1) can provide polyamides having a high flexibility. Dimer acid may have unsaturated bonds, but since it is difficult to color, it is preferably hydrogenated to form all the carbon-carbon bonds into saturation.

The aliphatic diamine (B1) having <NUM> or more carbon atoms is formed from hydrocarbon only except for the amino groups, and is dimer diamine (<NUM> carbon atoms for example).

(B1) is dimer diamine because it can provide polyamides having a high flexibility even if its content is small. Dimer diamine can be produced by reaction of dimer acid with ammonia followed by dehydration, cyanation and reduction. Dimer diamine may have unsaturated bonds, but since it is difficult to color, it is preferably hydrogenated to form all the bonds into saturation.

In the polyamide of the present invention, units other than the unit formed from the aliphatic dicarboxylic acid (A1) having <NUM> or more carbon atoms and the unit formed from the aliphatic diamine (B1) having <NUM> or more carbon atoms mainly form hard segments.

A unit for constructing the hard segments is not particularly limited, but is a unit formed from a dicarboxylic acid (A2) having <NUM> or less carbon atoms and a unit formed from a diamine (B2) having <NUM> or less carbon atoms.

The dicarboxylic acid (A2) having <NUM> or less carbon atoms includes, for example, sebacic acid (<NUM> carbon atoms), azelaic acid (<NUM> carbon atoms), adipic acid (<NUM> carbon atoms), terephthalic acid (<NUM> carbon atoms), isophthalic acid (<NUM> carbon atoms), and orthophthalic acid (<NUM> carbon atoms). Among these, because the flexibility is improved, the dicarboxylic acid having <NUM> or more carbon atoms is preferably included.

Moreover, the diamine (B2) having <NUM> or less carbon atoms includes dodecanediamine (<NUM> carbon atoms), undecanediamine (<NUM> carbon atoms), decanediamine (<NUM> carbon atoms), nonanediamine (<NUM> carbon atoms), octanediamine (<NUM> carbon atoms), hexanediamine (<NUM> carbon atoms), butanediamine (<NUM> carbon atoms). Among these, because the flexibility is improved, a diamine having <NUM> or more carbon atoms is included.

In the present invention, the hard segments preferably consist of units composing a highly crystalline polyamide. The highly crystalline polyamide is preferably a semicrystalline polyamide consisting of an aromatic dicarboxylic acid and an aliphatic diamine, and includes, for example, polyamide 4T, polyamide 9T, polyamide 10T, and polyamide 12T, with polyamide 10T being preferred among these because of favorable balance between thermal resistance and crystallinity thereof. Therefore, for composing the hard segments, (A2) is preferably terephthalic acid, and (B2) is preferably butanediamine, nonanediamine, decanediamine, or dodecanediamine, and more preferably <NUM>,<NUM>-decanediamine.

When units for composing the hard segments are units composing a highly crystalline polyamide, the polyamide thus obtained has an improved thermal resistance and forms a structure highly phase-separated between the hard and soft segments, which improves the flexibility.

Soft segments formed of a unit formed from an aliphatic dicarboxylic acid (A1) having <NUM> or more carbon atoms and/or a unit formed from an aliphatic diamine (B1) having <NUM> or more carbon atoms tend to have a shorter segment length, compared with soft segments formed of polyether or polyester. As the soft segments are shortened in the segment length, it may be difficult to form a phase-separated structure with the hard segments. However, in the present invention, by selecting the units for composing the highly crystalline polyamide as the units composing the hard segments, a phase-separated structure can be formed even if the soft segment length is short.

The polyamide of the present invention does not include any segment formed of polyether or polyester that is likely to decompose upon polymerization. The polyether includes, for example, polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, and polyoxyethylene-polyoxypropylene glycol, and the polyester includes, for example, polyethylene adipate, polytetramethylene adipate, and polyethylene sebacate. Polyamides including segments formed of polyether or polyester may be decomposed when a polymerization temperature is elevated.

The polyamide of the present invention may include a terminal blocking agent for the purpose of adjusting the degree of polymerization, inhibiting decomposition of a product, inhibiting coloring, etc. The terminal blocking agent includes, for example, monocarboxylic acids such as acetic acid, lauric acid, benzoic acid and stearic acid, and monoamines such as octylamine, cyclohexylamine, aniline, stearylamine, etc. The terminal blocking agent may be used alone or in combination thereof. The content of the terminal blocking agent is not particularly limited, but is usually <NUM> to <NUM> mol% relative to the total molar amount of the dicarboxylic acid and the diamine.

The polyamide of the present invention may include additives. The additives includes fibrous reinforcing materials such as glass fibers and carbon fibers, fillers such as talc, swelling clay minerals, silica, alumina, glass beads and graphite, pigments such as titanium oxide and carbon black, antioxidants, agents for heat aging resistance, antistatic agents, flame-retardant agents, and flame-retardant auxiliaries. The additive may be included at the time of polymerization, or may be included by melt-kneading, etc., after polymerization.

The polyamide of the present invention is excellent in thermal resistance, and a melting point, which is an index of thermal resistance, needs to be <NUM> or higher, preferably <NUM> or higher, more preferably <NUM> or higher, and still more preferably <NUM> or higher.

The polyamide of the present invention is excellent in a flexibility, and a tensile elongation at break, which is an index of flexibility, is <NUM>% or more, more preferably <NUM>% or more, and still more preferably <NUM>% or more. A polyamide with a tensile elongation at break of less than <NUM>% may have insufficient performance as a flexible material.

The polyamide of the present invention has a shore-D hardness, which is an index of flexibility, preferably of <NUM> or less, more preferably of <NUM> or less, and still more preferably of <NUM> or less.

Further, the polyamide of the present invention also has a tensile elastic modulus, which is also an index of flexibility, preferably of <NUM> MPa or less, more preferably of <NUM> MPa or less, still more preferably of <NUM> MPa or less, and most preferably of <NUM> MPa or less.

The method for producing the polyamide of the present invention is not particularly limited, and the polyamide can be produced by a normal polymerization method including, for example, polymerizing raw material monomers by removing condensed water from the system while heating them in a pressure vessel equipped with a stirrer or a continuous polymerization facility.

A catalyst may be used in the production of the polyamide of the present invention, if necessary. The catalyst includes, for example, phosphoric acid, phosphorous acid, hypophosphorous acid or a salt thereof. The content of the catalyst is not particularly limited, but is usually <NUM> mol% or less based on the total molar amount of the dicarboxylic acid and the diamine.

Moreover, in the production of the polyamide of the present invention, an organic solvent or water may be added as needed.

In the production of the polyamide of the present invention, the polymerization may be carried out in a closed system or at normal pressure. When it is carried out in the closed system, since the pressure may increase due to volatilization of the monomer or generation of condensed water, etc., the pressure should be preferably appropriately controlled. On the other hand, when the boiling point of the monomer used is high and the monomer does not flow out of the system without pressurization, it can be polymerized at normal pressure. When the raw material monomers are, for example, a combination of dimer acid, dimer diamine, terephthalic acid, and decanediamine, it can be polymerized at normal pressure.

In the production of the polyamide of the present invention, it is preferred to carry out the polymerization in a nitrogen atmosphere or in a vacuum in order to prevent oxidative deterioration.

The polymerization temperature is not particularly limited, but is usually <NUM> to <NUM>. In order to inhibit the decomposition and deterioration reaction of the obtained polyamide, the polymerization is preferably carried out at a temperature not exceeding <NUM>.

In the production method of the present invention, it is preferred to carry out the polymerization at a temperature equal to or lower than the melting point of the polyamide. When polymerized at a temperature equal to or lower than the melting point of the polyamide, the hard segment component remains precipitated, however the soft segment component is in a molten state, so that the entire reaction product has its fluidity. Therefore, the polymerization can be carried out with an existing melt polymerization equipment and by a conventional process for the polyamide. In this case, the polymerization of the hard segments proceeds in a state like solid phase polymerization. The method for polymerizing at a temperature equal to or below the melting point is particularly effective in polymerization of a polyamide having a high melting point of <NUM> or higher at which the polyamide is likely to decompose due to the high polymerization temperature.

The polyamide after polymerization may be extruded into strands as pellets, or may be hot-cut or underwater-cut into pellets.

In the manufacturing method of the present invention, solid phase polymerization may be further carried out in order to increase a molecular weight. The solid-phase polymerization is particularly effective when a viscosity at the time of polymerization is high, the operation becomes difficult, etc. The solid-phase polymerization is preferably carried out by heating at a temperature lower than the melting point of the resin for <NUM> minutes or longer under a flow of an inert gas or under reduced pressure, and it is more preferably carried out by heating for <NUM> hour or longer.

The polyamide of the present invention can be formed into a molded body by an injection molding method, an extrusion molding method, a blow molding method, a sintering molding method, etc. Of these, the injection molding method is preferable because it has a large effect of improving mechanical properties and moldability. The injection molding machine is not particularly limited, and includes, for example, a screw in-line type injection molding machine or a plunger type injection molding machine. The polyamide heated and melted in a cylinder of the injection molding machine is weighed for each shot, injected into the mold in a molten state, cooled and solidified in a predetermined shape, and then taken out from the mold as a molded body. The heater set temperature during injection molding is preferably equal to or higher than the melting point.

When the polyamide of the present invention is heated and melted, it is preferred to use pellets that have been sufficiently dried. If the amount of water contained in the pellets is large, it may foam in a cylinder of the injection molding machine, making it difficult to obtain an optimum molded body. The water content of the pellets used for injection molding is preferably less than <NUM> parts by mass and more preferably less than <NUM> parts by mass with respect to <NUM> parts by mass of the polyamide.

Since the polyamide of the present invention has an excellent flexibility and a high melting point, it can also be used as a heat-resistant elastomer. Specifically, it can favorably be used for automotive parts such as fuel tubes, brake pipes, intake/exhaust system parts, etc., intake/exhaust system pipes, and vibration damping materials; electrical and electronic parts such as pipes, seats, and connectors; gears, valves, oil pans, cooling fans, radiator tanks, cylinder heads, canisters, hoses, deformed materials, injection molding products, sheets, films, monofilaments for 3D printer modeling and fishing threads, fibers, etc..

The present invention will be described in more detail with reference to the following examples.

The characteristics of polyamides were obtained by the following methods.

The pellets and powder obtained were analyzed by <NUM>H-NMR using a high-resolution nuclear magnetic resonance apparatus (ECA-500NMR manufactured by JEOL Ltd. ), and the resin composition was determined from the peak intensity of each copolymer component (resolution: <NUM>, solvent: mixed solvent with a volume ratio of deuterated trifluoroacetic acid and deuterated chloroform of <NUM>/<NUM>, temperature: <NUM>).

A few mg of the obtained pellets and powder was sampled, and a temperature of the sample was raised to <NUM> at a heating rate of <NUM>/min by using a differential scanning calorimeter DSC-<NUM> (manufactured by PerkinElmer, Inc. ), then held at <NUM> for <NUM> minutes, lowered to <NUM> at a cooling rate of <NUM>/min, and further held at <NUM> for <NUM> minutes. The top of the endothermic peak observed when the temperature of the sample was raised again at a heating rate of <NUM>/min, was defined as a melting point.

The thermal resistance was evaluated from the measurement value of the melting point according to the following criteria.

By using the obtained pellets and powder, measurement was carried out at <NUM> and a load of <NUM> kgf according to JIS K7210.

After the obtained pellets and powder were sufficiently dried, they were molded by using an injection molding machine under the conditions of a cylinder temperature of <NUM> and a mold temperature of <NUM>, and test pieces (dumbbell pieces) for measuring general physical properties conforming ISO standard were fabricated. By using the obtained test piece, the tensile strength, tensile elastic modulus, and tensile elongation at break were measured according to ISO178.

A flexibility was evaluated from the measurement value of tensile elongation at break according to the following criteria.

Moreover, the flexibility was evaluated from the measurement value of tensile elastic modulus according to the following criteria.

By using the test pieces obtained in (<NUM>) above, measurement was carried out in accordance with ASTM D <NUM>.

A flexibility was evaluated from the measurement value of Shore-D according to the following criteria.

The following materials were used as dimer acid and dimer diamine.

In a reaction vessel equipped with a heating mechanism and a stirring mechanism, <NUM> parts by mass of dimer acid, <NUM> parts by mass of dimer diamine, <NUM> parts by mass of terephthalic acid, <NUM> parts by mass of <NUM>,<NUM>-decanediamine, and <NUM> parts by mass of sodium hypophosphite monohydrate, were charged.

Thereafter, the mixture was heated to <NUM> with stirring, and polymerization was carried out under a nitrogen stream at normal pressure and <NUM> for <NUM> hours while removing condensed water from the system. During the polymerization, the system was in suspension.

After completion of the polymerization, the product was removed, cut and dried to obtain polyamide pellets.

Polyamide pellets were obtained by carrying out the same operation as in Example <NUM> except that the monomers to be charged into the reaction vessel were changed as shown in Tables <NUM> and <NUM>. Examples <NUM>, <NUM>, <NUM> and <NUM> are not according to the claimed invention.

In a reaction vessel equipped with a heating mechanism and a stirring mechanism, <NUM> parts by mass of dimer acid, <NUM> parts by mass of dimer diamine, <NUM> parts by mass of adipic acid, <NUM> parts by mass of <NUM>,<NUM>-hexanediamine, and <NUM> parts by mass of sodium hypophosphite monohydrate were charged. Thereafter, the mixture was heated to <NUM> under sealing with stirring, and polymerized at <NUM> for <NUM> hours. Then, the pressure was gradually lowered to normal pressure, and the polymerization was further carried out for <NUM> hour. During the polymerization, the system was in suspension.

After the polymerization was completed, the product was removed, cut and dried to obtain polyamide pellets.

Into a powder stirring device equipped with a heating mechanism, <NUM> parts by mass of terephthalic acid and <NUM> parts by mass of sodium hypophosphite monohydrate were charged. While stirring heating at <NUM>, <NUM> parts by mass of <NUM>,<NUM>-decanediamine was added little by little over <NUM> hours to obtain a nylon salt. Then, the nylon salt was heated to <NUM> with stirring, and polymerization was carried out under a nitrogen stream at normal pressure and <NUM> for <NUM> hours while removing condensed water from the system. During the polymerization, the system was in powder form.

After completion of the polymerization, the product was removed to obtain polyamide powder.

Into a reaction vessel equipped with a heating mechanism and a stirring mechanism, <NUM> parts by mass of dimer acid, <NUM> parts by mass of dimer diamine, and <NUM> parts by mass of sodium hypophosphite monohydrate were charged.

Subsequently, the mixture was heated to <NUM> while stirring, and polymerization was carried out under a nitrogen stream at normal pressure and <NUM> for <NUM> hours while removing condensed water from the system. During the polymerization, the system was in a uniform molten state.

<NUM> parts by mass of polyoxytetramethylene glycol (PTMG1000) having amino groups instead of the hydroxyl groups at both ends, and having number average molecular weight of <NUM>, <NUM> parts by mass of terephthalic acid, <NUM> parts by mass of <NUM>,<NUM>-decanediamine, and <NUM> parts by mass of sodium hypophosphite monohydrate were charged in a reaction vessel equipped with a heating mechanism and a stirring mechanism, heated to <NUM> with stirring, and polymerization was carried out for <NUM> hours under a nitrogen stream at normal pressure and <NUM> while releasing generated water vapor. During the polymerization, the system was in suspension.

After completion of the polymerization, the product was removed, cut and dried, however, the polymerized product was brittle and unsuitable for practical use.

Tables <NUM> and <NUM> show the charging compositions of the polyamides, and Tables <NUM> and <NUM> show the characteristics of the obtained polyamides.

Since the polyamides of the Examples have a total content of <NUM> to <NUM>% by mass of the unit formed from the aliphatic dicarboxylic acid (A1) having <NUM> or more carbon atoms and the unit formed from the aliphatic diamine (B1) having <NUM> or more carbon atoms, all of these each has the excellent flexibility, melting point of <NUM> or higher, and excellent thermal resistance.

Because the polyamide of Comparative Example <NUM> did not include any unit formed from (A1) or any unit formed from (B1), and thus did not have any soft segment, and because the polyamide of Comparative Example <NUM> had a total content of less than <NUM>% by mass of the unit formed from (A1) and the unit formed from (B1), both were inferior in flexibility.

Claim 1:
A flexible polyamide comprising a unit formed from a dicarboxylic acid (A2) having <NUM> or less carbon atoms, a unit formed from an aliphatic diamine (B1) having <NUM> or more carbon atoms which is dimer diamine and a unit formed from a diamine (B2) having <NUM> to <NUM> carbon atoms,
wherein the polyamide
optionally comprises a unit formed from an aliphatic dicarboxylic acid (A1) having <NUM> or more carbon atoms,
has a total content of <NUM> to <NUM>% by mass of the unit formed from the optional aliphatic dicarboxylic acid (A1) having <NUM> or more carbon atoms and the unit formed from dimer diamine (B1),
comprises no segments formed of polyether or polyester, and
has a melting point of <NUM> or higher and a tensile elongation at break of <NUM>% or more, as measured according to the description.