DE1815192C3 - Process for the production of polyxylylene adipamide threads - Google Patents

Description

The invention relates to a process for the production of polyxylylene adipamide threads by melt spinning a condensation polymer of adipic acid and m-xylylenediamine or m- / p-xylylenediamine with a p-xylylenediamine content in the diamine mixture of less than 30 mol percent at spinning temperatures below 290 ° C, cooling the freshly spun filaments and drawing the filaments to more than three times their length at 70 to 90 ° C while the water content of the filaments is maintained less than 4 ⁰ Zo.

The polyxylylene adipamides described above are already known, and it is also known from these fibers, which are referred to as "MXD-6" fibers, to produce (see. US Pat 29 87 506, 29 97 463 and 32 00 183). Since these polymers, however, have a relatively low thermal stability and are difficult to use, they have not been able to use them in a satisfactory manner industrial production of MXD-6 fibers are used.

The object of the invention is therefore to create a process for the production of polyxylylene adipamide fibers by melt spinning, during which no thermal decomposition of the molten material occurs, threads with a high degree of whiteness as well as a high mechanical strength can be obtained.

In a process of the type described at the outset, this object is achieved in that the melt contains a non-volatile hydroxyl compound in an amount of 0.05 to 0.7 mol per kg of polymer and / or water, that the spinning temperature T satisfies the following equation:

265

<290,

0)

55

where X denotes the content of p-xylylenediamine in the diamire mixture in mol percent, and that the freshly spun threads are cooled by means of a cooling gas which flows at a flow rate of less than 1 m / s.

By adhering to the three parameters described, namely the addition of a non-volatile hydroxyl compound in the specified amount and, or water, setting the spinning temperature as well Cooling the freshly spun threads by means of a cooling gas under the specified conditions in the melt spinning of polyxylylene adipamides of the specified type, for example from the said US-PS is known to obtain strong threads with a high degree of whiteness. The strength of the threads produced according to the invention are more than 5 g / den. The threads obtained are in compliance of the mentioned conditions completely evenly.

A highly pure polymer is preferably used to carry out the process according to the invention used. For example, a polymer is used that meets the following conditions:

1.70 ^ r, _nl ^

1.11 - 1.052 r
1 - 0.984 r

where i] _{rcl denotes} a relative viscosity which at 25 ° C. using a solution of 1 g of the polymer dissolved in 100 ml of 96% strength sulfuric acid, and r is the ratio of the number of moles of the polyamide salt constituents as used in the Preparation of the polymer used, to the sum of the number of moles of the polyamide salt constituents mentioned and the viscosity stabilizers

Number of moles of polyamide salt components

Number of moles of polyamide salt constituents -I- number of moles of viscosity stabilizers

) ■

In the equation (2) shows the right side

1.11 - 1.052 r \ 1 - 0.984 r )

indicates that when the quantity »r« approaches 1 (where no stabilizer was used) η _η1 can be chosen in a wider range. If r = 1, the desired polymers are those with η _{Γ (!} Ι ~ 1.7 to 3.6. If, on the other hand, r becomes smaller, then the d> .r range for »? _{Rf (} , which is selected for obtaining preferred polymers can, narrower, and if r is not larger than 0.95, the left side, t] _rcl = 1.7 of the formula (2) cannot be satisfied.

13 15 192

Furthermore, the relationship between relative viscosity (> / „;) and the amount of end groups of the > MXD-6 «polymers investigated and found that if the extent of the polymerization reaction in the is kept substantially at 0.988 ± 0.03, a polymer can be obtained which has the equation (2) satisfied.

It has also been found that to obtain a satisfactory polymer by adjusting ^ these j; _rc; or the extent of the reaction, a method in which condensation polymerization is carried out by heating the reaction mixture under high vacuum (as usually used in the polymerization of polyamides, polyesters, etc.) must be avoided. For example, the desired setting cannot be brought about with the conventional processes for the production of “MXD-6” polymers, as described in the exemplary embodiments of US Pat. No. 2,766,221 and 2,997,463.

It has been found that the desired adjustment can be effected in a process in which the polycondensation reaction in the presence of steam or water vapor in contact with the molten polymer is carried out. In this case, atmospheric pressure or a Pressure is slightly above or below atmospheric pressure. This can reduce the extent of Polycondensation reaction almost theoretically from the water equilibrium curve between the vapor phase and the molten polymer in the reaction apparatus and from the kinetics of the rate of polycondensation with reversible reaction (G. V. Schulz: Z. Physik Chem., A 182, 127, 1938) can be set.

An aqueous solution of xylylene adipate was placed in an autoclave. The water was gradually removed while the internal pressure was kept below 4 to 10 kg / cm ² at 120 to 180 ° C. After the pressure increase was completed, the autoclave was closed and the temperature was increased to 260 to 280 ° C, and the reaction was completed at an internal pressure of 20 to 0 kg / cm ² . The molecular weight of the resulting "MXD-6" polymer (η _{Τ (1} = 1.70) was approximately 10,000. This is a polymer of the lowest molecular weight which can be satisfactorily spun into threads according to the invention.

In order to adjust the values of r and 7j _rPl (ie essentially the extent of the reaction) it is independent of the absolute value of η _η . _{ especially important to maintain a substantial equilibrium amount of water in the molten polymer.

When the polymerization reaction continues will happen until. the magnitude of the reaction becomes higher than 0.992, side reactions would be complicated in character occur in the molten polymer, causing gelation and / or discoloration of the polymer cause. Such side reactions are also related to the melt viscosity of the molten one Primary in connection.

Hypophosphorous acid or metal salts of the hypophosphorous acid are preferably used in the polymer melt Acid added in an amount of 10 to 1000 ppm to improve the whiteness. Of the metal salts are sodium and potassium. Calcium, zinc, aluminum, or manganese Cobalt salts mentioned. The amount of 10 to 1,000 ppm added is calculated as hypophosphorous acid. The addition is preferably carried out before or during the polycondensation stage in order to avoid discoloration to avoid the polymer during the reaction and to ensure uniform distribution. However, it is also possible to use the compounds mentioned during the melting and the To add spinning.

ίο Of the non-volatile that can be used according to the invention Hydroxyl compounds are aliphatic alcohols, for example propyl, butyl or octyl alcohol, Ethylene glycol, glycerine, pentaerythritol, neopentyl glycol, Pyrogallol or cyclohexyl alcohol, saccharides, for example glucose or cellobiose, or mixtures thereof are mentioned. These compounds are added in an amount of from 0.05 to 0.7 mol / kg of the polymer, since when used in an amount outside this range a Gel formation can occur.

The water content can for example be 0.14 mol / kg of the polymer when spinning a polymer with a relative viscosity η _{ΓίΙ of approximately 2.0 at 275 ° C.}

After spinning and cooling, the non-entangled threads are drawn to 3 to 5 times their length at 70 to 90 ° C., while the water content is kept below 4%, preferably at about 3 ⁰ zo. If desired, the drawn threads can be set in a conventional manner. If the water content in the threads exceeds 4%, undesirable over-stretching phenomena often occur. If the humidity continues to increase, the thread will crystallize and become difficult to draw. the

3S stretching and heat fixation can be applied to carried out in the usual manner (for example, as in US Pat. No. 3,200,183).

The quality of the polymer and the quality of the melt spinning can be determined by the number of knots in the drawn threads and also by the drawability. The most important factor form * the absolute amount of degraded polymer contained in the threads. This can also be done by assess the amount of insoluble polymer

<5 den when the thread is dissolved in formic acid. The relative measurement can be made by measuring the fluorescence intensity of the polymer solution (in formic acid) be performed.

The part which is insoluble in formic acid is a gel

jo polymer, which is produced when a secondary or side reaction has occurred to some extent. Even those soluble in formic acid In polymers, fluorescence will also occur if a side reaction has taken place. It is assumed

;> 5 men that the fluorescence is due to the presence of heterogeneous double bonds formed by the side reaction caused. It has been found that the by addition of sub-phosphoric acid thread produced for polymer melt is not only excellent in terms of whiteness, but also has a low fluorescence intensity compared to polymers without the additive mentioned. Therefore, it is believed that this additive also has a beneficial effect in preventing the Has the occurrence of secondary reactions.

The knots observed in the drawn threads represent a local, thick part with an approximate 1.5 to 2 times the diameter compared to the

18 15 1S2

normal part of the threads and are less than a few mm in length. It is known that such knots occur in polyamide threads and other synthetic threads, but on the order of only 0 to 5 knots per 10 degrees. However, in the case of a polyxylylene adipamide, there is a strong tendency for gelation to occur during melt-spinning, so it is was common to the conventional "MXD-6 <- threads nodes in the order of a few hundred or a few thousand nodes per 10 ⁿ are m. In order to prevent the formation of knots, the presence and amount of the hydroxyl compound in the molten state is very important. In the novel process it is possible, "MXD-o" filaments with a number of nodes below 15 per 10 m ^fi manufacture.

Claims (2)

Patent claims: 1. A process for the production of polyxylylene adipamide threads by melt spinning a condensation polymer from adipic acid and m-xylylenediamine or m- / p-xylylenediamine with a p-xylylenediamine content in the diamine mixture of less than 30 mol percent at spinning temperatures below 290 ° C, cooling the freshly spun threads Drawing the threads to more than three times their length at 70 to 90 ° C, while the water content of the threads is kept less than 4%, characterized in that the melt contains a non-volatile hydroxyl compound in an amount of 0.05 to 0, 7 mol per kg of polymer and / or water contains that the spinning temperature T satisfies the following equation: 265 + 0.33Z ^ T ⁰ C ^ 290, where X denotes the content of pX> lylenediamine in the diamine mixture in mol percent, and that the freshly spun threads are cooled by means of a cooling gas which flows at a flow rate of less than 1 m. 2. The method according to claim 1, characterized in that the polymer melt hypophosphorous Acid or metal salts of hypophosphorous acid are added in an amount of 10 to 1000 ppm.