JPH01263126A - Molded polyamide product and its production - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to molded articles containing polyamides consisting primarily of tetramethylene adipamide units and having improved properties.

Conventional technology Molded products containing polyamide mainly consisting of tetramethyleneazino and mido units are disclosed in European Patent No. 0038.
No. 582. The moldings exhibit superior properties compared to moldings containing polyamides of polyamide 6 or 6.6, especially with respect to hardness at high temperatures and impact resistance at low temperatures. However, due to ever-increasing specifications, especially for use at high temperatures, the molded polyamide products of EP 0 938 582 sometimes fail to meet specifications.

Problems to be Solved by the Invention Currently, research is directed toward molded articles containing polyamides mainly consisting of tetramethylene adipamide units and having further improved properties, and methods for producing these molded articles. A polyamide consisting of a moderate amount of tetramethylene adipamide was found, the moldings of which exhibited excellent properties.

A molded article containing a polyamide consisting mainly of tetramethylene adipamide units according to the invention has a melting enthalpy greater than the enthalpy of fusion measured after subsequent solidification of the polyamide? The increased crystallinity of the polyamide, expressed as the first enthalpy of fusion, which is at least 30 J per cent. M,
11 The enthalpy of fusion was measured using a differential scanning calorimeter (DSC) on a sample of the molded article at a heating rate of 5°C/min, and the second enthalpy of fusion was measured by cooling the molten polyamide to below its crystallization temperature at a cooling rate of 5°C/min. , after complete solidification and after heating again at a heating rate of 5° C./min.

During the DSC measurements, it also prevents the measurement of the melting enthalpy. f? If the condensation of IJ amide is a raw material, the sample must be placed in a pressure-tight sealed container that prevents evaporation of water produced by condensation and polycondensation. Otherwise, too large a value of the melting enthalpina will be obtained. Furthermore, for samples with low molecular weight (η<about 2.5), post-condensation during DSC measurements will affect the value of ΔHm and must be corrected.

A molded article is a product formed from a melt state by injection molding, melt extrusion molding, Soles molding or injection molding, and does not contain filaments or films.

Preferably the first enthalpy of fusion is at least +5 J/? greater than the second enthalpy of solution. More preferably, the difference is at least 60 J//.

1 g dissolved in 100 M of 96% sulfuric acid at 25°C
The molecular weight of a polyamide, expressed as its relative viscosity measured in a solution of
Measured by melting viscosity.

The polyamide must consist of tetramethyleneadipamide units, for example at least 80%. A high content of copolymer units is generally not acceptable since in this case the polyamide exhibits amorphous properties resulting in a low absolute level of improved properties. However, if isomorphic groups such as inphthalic acid and/or polybutylene terephthalic acid are introduced, higher contents are permissible. The copolymer units can be, for example, polyamide-forming units such as dicarboxylic acids, diamines and lactams, imide-forming groups and ester-forming groups.

The polyamides may contain additives such as stabilizers, flame retardants, reinforcing fillers such as inorganic or organic fibers, mold release agents, colorants, pigments and other polymers.

Molded articles containing polyamides according to the invention have a significantly higher elastic modulus, lower creep, lower water absorption, sufficient oxidative stability and stress cracking resistance compared to molded polytetramethylene articles according to the prior art.

The Gaymans are from Japantegrat ton of
FundamentazPotyBer 5cienc
e and Technology [L, A.

Edited by KzeintJes, P. J. Lemstra, pozyirprscience and tee
Bulletin of the International Conference on Hnozogy (Netherlands,
April 14-18, 1985, pp. 573-576)
,Ezsev i erAppzled 5cienc
e Publication (New York, London) 1987] give examples of polyamide 4.6 filaments and films with high first enthalpies of fusion.

5AXS Gaymans, it is determined that microcrystalline growth is responsible for the increase in crystallinity. However, increased crystallinity due to microcrystal growth has a negative effect on the impact resistance of polyamide products, resulting in brittleness. This is T, J, f3essett and others: Journaz
of Materials 5science [10th
Vol. 1137-1136 (1975), see for example FIG. In this, the tenacity of polyamide 6 decreases sharply when the degree of crystallinity increases by 10%.

Surprisingly, it has been found that the molded polyamide articles with increased crystallinity according to the invention exhibit significant impact resistance. Increased crystallinity 70J/? Even at an Izot impact resistance of about 7 J/rn, which is better than that of other polyamides, such as nylon 6.6 or 6.
Becomes 1.

The torsional pendulum modulus at high temperatures is increased by a factor of more than 2 compared to products according to the prior art, for example as described in EP 0 938 582.

In the method for producing a molded article of the present invention, the product obtained by molding from a molten state is subjected to heat treatment at a temperature of 18 degrees below the melting point after solidification.

Preferably, a polyamide consisting primarily of tetramethylene adipamide units (the first enthalpy of fusion of the polyamide is at least 30 joules per 2t?--greater than the enthalpy of fusion measured after subsequent coagulation of the lyamide) The method for producing the molded article containing the polyamide consists of molding the molded article from the molten state and, after subsequent solidification, heating the molded article at a temperature between 220° C. and the melting temperature of the polyamide.

The product can be formed from the melt by any method, such as injection molding,
This can be done by extrusion molding, press molding or injection molding.

The time of heat treatment may vary within a wide concave range and depends, among other things, on the molding conditions, the dimensions of the product and the temperature level of the heat treatment. In practice times are usually up to 2+ hours, but heat treatments of less than 1/2 hour are usually ineffective.

Use of temperatures below 220°C has no effect.

This is because in this case, it takes a long time for the treatment to be effective. In contrast, the use of temperatures below the melting point of the polyamide results in product distortion.

Preferably, the temperature is 240 to 285°C. The processing time should be at least 4 minutes per minute to remove the product from the melt, depending on the method used to form the product.
Cooling at a rate of 0°C can significantly shorten the time.

Preferably the cooling rate is at least 100°C per minute. Additionally, the use of hydrostatic pressure increases the speed of the process.

As a side effect, the molecular weight of the polyamide increases during heat treatment, but the increase in molecular weight has only a minor effect on the unexpectedly large improvement in the properties of the polyamide.

This heat treatment must not be combined with stress relaxation of the product mixture by heating at increased temperatures (although this temperature is generally significantly lower). This process is described, for example, in U.S. Pat.
It is described in the specification of No. 17.

For polyamides such as nylon 6 and 6.6,
Generally this temperature is below 180°C.

It is advantageous to subject the product to the heat treatment according to the invention immediately after shaping and before complete cooling, so that only a small amount of heat is required to bring the product to the required temperature. The heat treatment is preferably carried out in an atmosphere containing a large amount of water vapor, for example up to 50 volumes.

Another outcome of heat treatment is that a uniform product is obtained. This is especially the case with thick-walled products. However, due to rapid cooling, for example in the case of injection molding, the surface layer of the treated product has a very high degree of crystallinity, which is an unexpected advantage of the invention.

Example of fruit decoration The following test method was used.

(a) Measurement of the first and second enthalpies of fusion: Using a differential scanning calorimeter (D
SC), -j -* y (Perkin) and x q - (Ezmer) 0DSC2°Temperature range 30~
Heating and cooling rate 5°C/min for 315°C.

)Measurement of melting point: Peak temperature from SC as described in (a).

(C) Relative viscosity (ηret): A solution of 1, P dissolved in 96% by weight sulfuric acid 1001 at 25°C.

(b) Torsional pendulum modulus G' at a heating rate of 1° C./min and a number of images of 0.2153H.

(e) Izot Impact Resistance ASTM 256° Experiment 1 The test bar was 5TANYL TW 300■ (medium flow, ηret=3.5, DSM Nio y 4.6,
Injection molded from Netherlands). Temperature of melt #310”
Temperature of O1 type is 60℃.

Does the test bar contain 1 water vapor and 10 volumes of water? Heat treatment is performed at 260°C in an elementary atmosphere. Measure the properties of the test bar at different time intervals.

Comparative Example A O3,478812g0288 10 Example 1
2 3.7 120 83297288 Example 2 +
3.9 129 823002899.3 The drawings include:
The elastic modulus (torsion pendulum modulus) as a function of temperature for Examples 1 and 3 is shown graphically. This graph includes
Data for Comparative Example A and a number of other injection molded thermoplastics are provided. Data for other thermoplastics are H, M
.

J. C. Creamers: Kunststof en.
Rubber (1985) pp. 21-32 - FIG.

It is clear from this experiment that a sample of nylon 4.6 with high crystallinity according to the present invention exhibits a significant increase in torsional pendulum modulus compared to a sample with comparable first and second enthalpies of fusion. It is. The impact resistance is
Even though the enthalpy of fusion is almost doubled, it is only slightly affected. Furthermore, the second
The enthalpy of fusion is almost unaffected.

Experiment 2 (worker, comparative example 2A) Actual Mlt-<D returns, but 5TANYL TW 300■
Glass fiber filled (30% by weight) nylon instead of 4.
6 was used. In this case as well, a product with extremely high crystallinity could be obtained.

The following properties of ff1K that had been heat-treated for a period of time were measured.

ΔHml=134J/? (97)-Tml=292℃(294)Izot=10J/
rn%G'f'250"0)=1.0.103MPa
(0,7,103) and this number is the value of the untreated product (0 hours) (Comparative Example 2A).

The modulus of elasticity of glass fiber-filled products is generally determined primarily by the filler material, and a significant increase in the modulus of elasticity is observed (approximately 40%).

Experiment 3 (Example 5, Comparative Example 3A) A tube with an outside diameter of 7n and a wall thickness Q, f3 Im was extruded from polyamide wood, 6 (ηret” 3.8, stabilized with Cu). Heat treatment was carried out at ℃ for 20 hours.The mechanical strength of the tube was determined by inserting a tube of a certain length between parallel plates and measuring the displacement of the plates as the effect of the force of the plates. Untreated) 78.4 80 286.) 288 0.1
9 0.34 example 5 (processing) 157.682 310 2B9 0.15
0.18 Polyamide according to the invention, especially at high temperatures 4.6
It is clear that a tube with a sufficient elastic modulus:
It is.

Experiment 4 (Example 6, Comparative Example 4A) The goal bearing cage (diameter 6 cfIL) was made of polyamide + containing 30% glass fiber and 1% by weight and heat stabilizer.
, 6 (η, et = 3.3′).

After injection molding, heat the ball bearing cage to 260°C.
Heat treatment is performed for 20 hours. Mechanical strength, for pipes (
Measured using the same method as experiment 3) (untreated) Example 6 (treated) 153 7.0 3
．． 4 Improvements are also obtained with this glass fiber.

Experiment 5 (Example 7, Comparative Examples 5A and 5B) Filling a thin-walled electrical connector with clay (70% by weight)
injection molding from polytetramethyleneazino9amide. The relative viscosities of these were 3.4 and 2.4, respectively.

For molding high molecular weight polyamides, relatively high pressures and melt temperatures were required to obtain complete filling of the mold. The connector showed discoloration. Product ηret is 2.9
(Comparison flJ5A).

In the case of low weight polyamide compositions, injection molding was easy due to good flow of the polyamide. However, the resulting connector was brittle and could be easily crushed by hand.

'Jret was 2.3 (Comparative Example 5B).

The subsequent connector was heat treated at 260° C. for 3 hours in a moist (10 volume-i) nitrogen atmosphere (Example 7). After processing, the connector showed no brittleness. ηret increased to 2.9. However, the elastic modulus of this connector was more than that of the comparative fil A connector.

According to USC, the first enthalpy of fusion is 1.26 J/l'' for heat-treated connectors and compared f1-+ 5
In the case of A, it ran at 96 J/l.

Starting Materials Heat Treated Final Product Example 7 η = 2° + 2.9 Adequate Mechanical Strength Comparative Example 58 η = 2.4 − 2.3 Low Mechanical Strength Experiment 6 Test bars were melt-pressed from 5TANYL TW300R However, the molds were cooled at different cooling rates.

After solidification and cooling until a temperature of 100 °C is obtained, the product is heated to 260 °C and at this temperature 2
Holds time.

The crystallinity of different samples was determined by DSC.

Cooling rate ΔHml (℃/min) J/? In the case of low cooling rates, significantly longer heat treatments are necessary to obtain products with the crystallinity of the invention.

[Brief explanation of the drawing]

The drawing is a torsional thump mozoulus/temperature diagram. :1---2''

Claims (1)

Claims: 1. In a molded polyamide article consisting primarily of tetramethylene adipamide units, the first enthalpy of fusion, expressed as at least 30 units per gram, is greater than the enthalpy of fusion measured after melting and subsequent solidification of the polyamide. The first enthalpy of fusion is measured on a sample of the molded article with a differential scanning calorimeter (DSC) at a heating rate of 5°C/min, and the second enthalpy of fusion is determined by cooling the molten polyamide. Cool down to below its crystallization temperature at a rate of 5°C/min, then heat at a rate of 5°C after complete solidification.
Molded polyamide products measured after heating again at /min. 2. The first enthalpy of fusion is at least 4 g per g greater than the enthalpy of fusion measured after melting and subsequent solidification.
5. The molded polyamide article of claim 1, wherein the molded polyamide article has a weight of 5 joules. 3. Molded polyamide article according to claim 1 or 2, wherein the relative viscosity of the polyamide is at least 2.0 (1 g in 100 ml of 96% by weight sulfuric acid). 4.Izotz impact resistance at 25°C is at least 6KJ
/m^2 (dry as a molded body), according to any one of claims 1 to 3. 5. The method for producing a molded polyamide product according to any one of claims 1 to 4, wherein the polyamide product after molding is subjected to heat treatment at a temperature of 220 to 290°C for 0.25 to 24 hours in an inert gas atmosphere. . 6. The method according to claim 5, wherein the temperature is 240-285°C. 7. Claim 6, wherein the inert gas atmosphere contains water vapor.
Method described. 8. The product molding process is such that the product is removed from the melt at least 40 times per minute.
6. The method of claim 5, wherein the cooling is performed at a rate of .degree. 9. Claim 8, wherein the cooling rate is at least 100°C per minute.
Method described.