CS252997B1 - The way of determining the optimum ratio. for surface-colored polypropylene fibers - Google Patents

Abstract

The solution concerns a method for determining the optimal splitting ratio DPopt for surface-dyeable polypropylene fibers, when dye uptake from 80 to 90 wt. is achieved. The essence of the solution is to determine the birefringence of the unoriented fiber and to determine the optimal splitting ratio, the relationship DPopt = a — b(Anj is used, in which the empirical constants a and b are determined in advance from the dependence between the birefringence of various pre-oriented unoriented fibers and such splitting ratio of the oriented fibers prepared from them, when the highest dye uptake is achieved. The method for determining the optimal splitting ratio of surface-dyeable polypropylene fibers according to this solution can be used in the development of technologies for preparing surface-dyeable fibers of various fineness within the framework of small-tonnage production, in increasing the spinning performance of existing technologies, as well as in the transition to other types of polypropylene granulates.

Description

The solution relates to a method of determining the optimal elongation ratio for surface-dyeable polypropylene fibers.

The preparation process of surface-dyeable polypropylene fibers modified with nitrogen-containing ethylene acrylate modifiers consists of two main stages. In the first stage, the modifiers are added to polypropylene, which is spun and unoriented fibers are prepared. In the second stage, the fibers are deformed unidirectionally and oriented fibers are obtained, with the elongation ratio being determined based on the achievement of the required mechanical properties. When surface dyeing modified polypropylene fibers prepared in this way, cases of poor dyeing and therefore insufficient use of the present modifier often occur. This is the cause of the undesirable effect of color streaking in textile processing of fibers.

It has been found that polypropylene fibers modified with ethylene acrylate copolymers with nitrogen-containing modifiers are dyed differently depending on the degree of orientation. While unoriented fibers are dyed only in the surface layer, with increasing draw ratio, the dyeing of the inner areas increases and the amount of stably bound dye increases. After exceeding a certain draw ratio, the dyeing of the fibers decreases again. An increase in dye uptake in highly oriented fibers cannot be achieved either by modifying the dye bath or by extending the dyeing time. It follows from the above that for surface-dyeable polypropylene fibers there is one optimal draw ratio from the point of view of dyeing, when dyeing of the entire fiber cross-section can be achieved and sufficient use of the modifier present is ensured, and at the same time the amount of stably bound dye is from 80 to 90% by weight. The optimal draw ratio of surface-dyeable polypropylene fibers is related to the overall pre-orientation of the unoriented fibers. In order to achieve the same resulting color effect, it is necessary to draw oriented fibers to a higher draw ratio, while pre-oriented fibers to a lower draw ratio. Such behavior of surface-dyeable polypropylene fibers in the surface dyeing process is not in accordance with the previously known knowledge about the dyeing process of polyester, polyamide and polyacrylonitrile fibers. In these types of fibers, unoriented fibers are dyed best, and with a gradual increase in the draw ratio, their dyeing ability gradually decreases.

The essence of the solution is a method of determining the optimal elongation ratio DP _opt for surface-dyeable polypropylene fibers modified with nitrogen modifiers, when dye uptake from 80 to 90% by weight is achieved. The solution consists in determining the birefringence of the undyed fiber Δη and using the relationship,

DP _opt = a — b(Anj in which the empirical constants a and b are determined in advance from the dependence between the birefringence of the pre-oriented non-directional fibers and such a directional ratio of the pre-oriented fibers prepared from them, when the maximum desired dye uptake is achieved in the range of 80 to 90 wt.%.

Surface-dyeable polypropylene fibers prepared under different spinning conditions, directed to DP _opt , are dyed uniformly throughout the cross-section and the amount of stably bound dye is only a function of the content of the modifier present. Their mechanical properties are suitable for further textile processing. Furthermore, it is advantageous to determine DP _opt when switching to other types of polypropylene granulates, as well as when changing the performance of the spinning equipment. The method of determining DP _opt for surface-dyeable polypropylene fibers according to this solution can be applied within the framework of the introduction of small-tonnage production of special types of fibers.

Example 1

To the melt of polypropylene (type TE 430 with a flow index of 25 g/10 min) was added 8 wt. % of ethylene acrylate copolymer with amine groups with a content of 2.2 wt. % nitrogen. After homogenization in a dynamic mixer, such a melt was spun at a temperature of 260 °C and several different levels of discharge V _o and winding V _L speed. Undirected modified polypropylene fibers were directed to different directing ratios at a temperature of 130 °C. The fibers prepared in this way were dyed from a bath containing the acid dye Sumlnol Fast Blue PR at a concentration of 2% by weight of the fiber. It was found that fibers with the same modifier content and different degrees of orientation contained different amounts of stably bound dye, which is shown in Table 1.

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Table 1

Conditional fiber. Student ratio Extract. dye. bath [%] Strength [cN/dtex] Ductility [%] Δη . 10 ³ weeks of fibers DP _op t _At ~ 13.72 m . min ^-1 1 : 2.5 40.1 2.3 85.5 1 : 3.0 62.3 2.7 48.1 V _L — 400 m . min ^-1 1 : 3.5 83.0 3.1 41.5 3.7 1 : 4.0 1 : 4.0 90.1 3.8 36.3 1 : 4.5 83.2 4.4 34.7 V _o = 20.58 m . min ^-1 1 : 2.5 45.3 2.5 61.3 1 : 3.0 67.1 2.9 58.2 V _L = 600 m . min ^-1 1 : 3.5 83.5 3.2 48.3 5.1 1 : 38 1 : 4.0 88.1 3.8 40.2 1 : 4.5 79.0 4.5 30.1 V _o — 27.44 m . min ¹ 1 : 2.5 55.1 2.6 62.4 1 : 3.0 70.3 3.0 59.2 V _L = 800 m . min ^-1 1 : 3.5 88.1 3.4 45.4 6.2 1 : 3.7 1 : 4.0 82.3 3.9 35.5 1 : 4.5 79.4 4.5 29.3 V _o = 34.30 m . min' ¹ 1 : 2.5 51.5 2.8 64.7 1 : 3.0 68.2 3.1 53.8 V _L = 1 000 m . min ¹ 1 : 3.5 89.1 3.5 41.7 8.1 1 : 3.6 1 : 4.0 87.2 3.9 32.3 1 : 4.5 75.1 4.6 26.2 _At ~ 41.16 m . min' ¹ 1 : 2.5 75.1 2.9 65.0 1 : 3.0 90.3 3.6 43.5 8.8 1 : 3.4 V _L = 1 200 m . min ^-1 1 : 3.5 88.1 3.9 25.1 1 : 4.0 78.2 4.7 23.5

The DP _opt values given in Table 1 for different spinning conditions were determined from the graphical dependences of the dye bath recovery and the elongation ratio of individual fibers. The mutual relations between the birefringence of undirected fibers and the determined DP _opt were processed by the linear regression method into the relationship

DPopt = a — b(An) where a = 4.3608 and b = 103.5771 with a correlation coefficient of 0.973. The relationship thus obtained is applicable for calculating the optimal distribution ratio from the point of view of dyeability of surface-dyeable polypropylene fibers when changing the technological conditions of spinning on the same spinning equipment or when changing the molecular weight of the granulate.

Example 2

Surface-dyeable polypropylene fibers were prepared as in Example 1 using a polymer with IT = 24.16 g/10 min, to which was added 8 wt. % of an ethylene acrylate copolymer with amino groups containing 1.95 wt. % nitrogen. With a dosage of 25 g/min, undyed fibers were prepared at varying draw speeds as shown in Table 2. Fibers with different degrees of pre-orientation evaluated by birefringence were obtained. According to the relationship given in Example 1, the optimal dyeing ratios to which the prepared fibers were dyed were calculated. According to the dyeing procedure as in Example 1, the amount of stably bound dye was determined.

Table 2

V _L [m/min] Δη . 10 ³ non-long fibers DP _About pt Dyeing bath yield (%] 947 11.69 3.15 86.8 728 9.94 3.33 89.3 653 8.82 3.44 88.2 591 8.16 3.51 90.4 541 6.44 3.69 91.3

Surface-dyeable fibers prepared by spinning at various draw speeds and directed to DP _opt are dyed with high bath yield.

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Example 3

Surface-dyeable polypropylene fibers were prepared as in Example 1 using polypropylene granulate with different molecular weights characterized by the flow index. With a dosage of 25 g per min and a draw-off speed of 591 m/min, undirected fibers were prepared, for which different birefringence was determined as a result of their different pre-orientation. According to the relationship in Example 1, the optimal directing ratios were calculated. The fibers directed on DP _opt were subjected to the dyeing process in accordance with the procedure in the previous examples. The results of determining the amount of stably incorporated dye are given in Table 3.

Table 3

Flow index η. 10 ³ [g/10 min] undeveloped. fibers

43.66 5.78

24.16 8.16

20.73 12.57

Surface-hardening fibers prepared from polypropylene granulate with different

DPopt Dyeing bath yield [%] 3.76 87.3 3.51 88.2 3.06 86.5

flux index and due to DP _opt are colored in the desired intensity.

Claims (1)

Ways to determine the optimum die draw ratio DT of _optical povrchovofarbiteíných nitrogenous modifiers modified polypropylene fiber intake dyes 80-90 wt.%, Characterized by determining the birefringence An nedíženého fibers and to determine the optimum die draw ratio DT _IP link is used t Y N O L E Z U DP _opt = a - b (An), in which the empirical constants a and b are predetermined depending on the relationship between the birefringence of the pre-oriented non-regrinded fibers and such a draw ratio of the different fiber fibers prepared therefrom to achieve the highest dye uptake.