METHOD FOR PRODUCING HOLLOW FILTER ROD OF PLA FIBER

TECHNICAL FIELD

[0001]The present invention relates to the technical field of hollow filter rods, in particular, the present application relates to a method for producing a hollow filter rod of PLA fiber.

BACKGROUND ART

[0002]With the increasing development of cigarette production technology, the types and appearance of cigarettes are more diversified. Cigarettes with unique shapes are more likely to be popular among people, thus resulting in the emerging of a new type of filter rod, the hollow filter rod.

[0003]It is a basically mature process to produce a pipe (hollow) filter rod with acetate fiber tows, most of which are made by high temperature steam heating and rapidly curing to produce filter rods. For example, a Chinese patent CN111436650A discloses a method for producing a hollow cooling filter rod, which consists of tows, a cooling material and a curing agent. The filter rod is prepared on a wire-drawing molding machine for hollow filter rod with a corresponding mold by adopting a production process of accelerated curing by means of high temperature steam. The solid external portion of the filter rod is of a smooth cylindrical structure with certain elasticity and hardness, suitable for cigarette tipping; the internal hollow part is of a straight-through empty cavity structure having a shape similar to a bellow, providing better thermal transfer and cooling effects when smoke passes therethrough. Due to the straight-through structure in the middle part of the filter rod, the suction resistance is also very low, and when used for a novel tobacco, the atomized amount of the cigarette is a two-fold increase while the temperature is reduced, so that the experience of a smoker is satisfied. Therefore, a new solution is provided for improving the quality of the cigarette and developing novel tobacco products.

[0004]Due to the fact that the PLA has the advantages of low price, easy degradation and no pollution compared with the acetate fiber, it is therefore very important to study the preparation of PLA filter rod. However, with respect to producing a pipe (hollow) filter rod with PLA tows, there is indeed a technology gap in the prior art.

[0005]Moreover, polylactic acid (PLA) is a thermoplastic aliphatic polyester with low glass transition temperature, and the case of rigidity and thermal collapse will occur under high temperature. In the early development of producing the pipe (hollow) filter rod with PLA tows, steam heating method is also used to trial-prepare a filter rod, but normal production cannot be carried out due to an over high steam temperature, poor effect, and an irregular shape of the filter rod.

[0006]Therefore, in order to solve the above problems, it is necessary to develop a reasonable and efficient method for producing a hollow filter rod of PLA fiber.

SUMMARY

[0007]The purpose of the present invention is to provide a method for producing a hollow filter rod of PLA fiber, in which the PLA fiber tows is heated by means of hot air heating to obtain the PLA fiber hollow filter rod after curing. It has good molding effect, proper regularity, and low pollution.

[0008]For achieving the aforesaid purpose, the present invention is implemented by adopting the following technical solutions:

[0009]A method for producing a hollow filter rod of PLA fiber, comprising the following steps:

[0010]Loosening PLA fiber tows, then feeding the PLA fiber tows into a molding cavity, and heating and curing-molding PLA fiber tows with heated air to obtain the hollow filter rod of PLA fiber.

[0011]Preferably, in the present invention, temperature of the heated air is in a range of 65° C. to 85° C.

[0012]Preferably, in the present invention, when the heated air is fed into the molding cavity, the heated air is pressurized by an air pump, and the air pump is electrically connected to a temperature sensing member in the molding cavity to adjust the output power of the air pump by obtaining real-time temperature in the molding cavity, such that the temperature in the molding cavity is between 65° C. and 85° C.

[0013]Preferably, in the present invention, a molding inner core is provided in the molding cavity, and the shape of the cross-section of the molding inner core comprises the shapes of a peach heart, a pentagram, a circle and a plum flower, such that the molded hollow filter rod of PLA fiber has a middle hole with the corresponding shape.

[0014]Preferably, in the present invention, the air is filtered before the air is heated.

[0015]Preferably, in the present invention, the total denier of the PLA tows ranges from 60000 d to 66000 d.

[0016]Preferably, in the present invention, the loosening is performed simultaneously with two strands of PLA tows, and the total denier of each strand of the PLA tows is in the range of 30000 d to 33000 d.

[0017]Preferably, in the present invention, when the PLA fiber tows are molded, the added amount of triacetin is in a range of 12%~16%.

[0018]The method for producing the hollow filter rod of PLA fiber according to the present invention has the following beneficial effects: the PLA fiber tows are heated by hot air heating, and the hollow filter rod of PLA fibers obtained after curing can achieve good molding effect, proper regularity, and low pollution.

BRIEF DESCRIPTION OF DRAWINGS

[0019]In order to more clearly illustrate the technical solutions in the examples of the present application, drawings used in the examples will be briefly introduced in the following. Obviously, the drawings described in the following are merely some examples of the present application, and for those skilled in the art, other drawings can be further obtained according to these drawings without inventive efforts.

[0020]FIG. 1 is a preparation flow schematic diagram of one example of the method for producing the hollow filter rod of PLA fiber according to the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0021]The technical solutions in the examples of the present application will be clearly and completely described in the following in combination with the drawings in the examples of the present application.

[0022]In the following section, the terms “first” and “second” are merely used for the purpose of illustration, and shall not be construed as indicating or implying their relative importance over others. The following section provides multiple examples of the present application, wherein different examples may be substituted or combined together with each other. The present application may therefore also be considered to contain all possible combinations of the same and/or different examples as described. Thus, if one example contains features A, B and C, and another example contains features B and D, then the present application should also be considered to comprise an example of all other possible combinations containing one or more of A, B, C and D, although such example may not be explicitly written and described in the following sections.

[0023]The following section provides examples and is not intended to limit the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements as described without departing from the scope of the contents of the present application. Various examples may appropriately omit, replace, or add various processes or assemblies. For example, the described method may be performed in a different order from those described, and various steps may be added, omitted, or combined. In addition, features described with respect to some examples may be combined into other examples.

[0024]Please refer to FIG. 1. The method for producing a hollow filter rod of PLA fiber according to the present application, the method comprises the following steps:

[0025]Loosening PLA fiber tows, then feeding the PLA fiber tows into a molding cavity, and heating and curing-molding PLA fiber tows with heated air to obtain the hollow filter rod of PLA fiber.

[0026]The heating and molding process of an acetate fiber filter rod is relatively mature, but the heating and molding process of PLA is very deficient. Due to the fact that compared with acetate fiber, PLA has the advantages of low price, easy degradation and no pollution, therefore the preparation study of the PLA filter rod is now of great importance. The present invention is emphasized on the heating production of the PLA fiber filter rod.

[0027]Moreover, due to the fact that most of the heating process for hollow filter rods of acetate fiber adopts steam heating, the steam temperature can reach more than 170° C. However, PLA is a thermoplastic aliphatic polyester with low glass transition temperature, resulting in a state of rigidity and thermal collapse under high temperature condition, it will get an extremely poor molding effect when producing the hollow filter rod of PLA by means of high temperature steam.

[0028]After a plurality of experiments and learnings thereof, it is found that it is impossible to use steam heating, for the temperature is required to be less than 100° C. for the heating production of the hollow filter rod of PLA, as a result the steam is condensed into water.

[0029]Therefore, we propose to directly adopt means of air heating for producing and molding the hollow filter rod of PLA, and it is experimentally verified to have high feasibility, details of which are as follows:

[0030]Heating air to a predetermined temperature followed by contacting the heated air with PLA fiber tows that are fed to a molding machine set after loosening, and heating and curing the PLA fiber tows to prepare the PLA filter rod.

[0031]Specifically, loosening the PLA fiber tows and then feeding the PLA fiber tows to the molding cavity. Meanwhile, also inputting the heated air into the molding cavity, such that the polyester fiber tows are in contact with hot air, thereby the polyester fiber tows are heated and cured to obtain the PLA filter rod by molding.

[0032]Since we need to prepare the hollow filter rod of PLA, the molding cavity should be provided with a molding inner core. The PLA fiber tows can reach the space between the outer side of the molding inner core and the inner side of the inner side wall of the molding cavity, and contact with the heated air to form the PLA hollow filter rod with a hollow hole (whose shape depends on the structure of the molding inner core).

[0033]Certainly, the shape of the cross-section of the molding inner core comprises the shapes of a peach heart, a pentagram, a circle and a plum flower, such that the molded hollow filter rod of PLA fiber has a middle hole with the corresponding shape.

[0034]Moreover, as the air feeding the molding cavity needs to be pure and at a predetermined temperature, it is filtered before the air is heated, that is to say, the air is first filtered by a filtering bin to ensure that it meets the standard of pure air, and then the pure air is heated and fed into the molding cavity.

[0035]Certainly, the aforesaid predetermined temperature, i.e., the temperature for heating PLA, or, the temperature range of the air feeding the molding cavity after heating, is in the range from 65° C. to 85° C.

[0036]The effect of different hot air temperatures on the molding and production of the filter rod, as well as the physical indicators and appearance of the filter rod were investigated, and the results are as follows:

[0037]That is to say, with respect to the production of the pipe (hollow) filter rod with the PLA tows, when the hot air temperature is below 60° C., there are poor production results such as a deformed filter rod, poor roundness and low hardness due to the fact that rapidly curing of the filter rod is unable to be implemented during the molding; when the hot air temperature is 65° C.~85° C., the production situation is normal, and the indicators and appearance of the filter rod meet the requirement; when the hot air temperature exceeds 90° C., the production condition becomes worse, wherein the roundness and coaxiality of the filter rod become worse. Therefore, the hot air temperature of 65° C.~85° C. is suitable for the production of the pipe (hollow) filter rod, which is much lower than the high temperature steam temperature used in the production of the acetate fiber filter rod.

[0038]Certainly, the inner side wall of a heating bin is provided with a heating wire and a temperature inductor electrically connected with an electric heating wire. Once the temperature deviates from the range of 65° C.~85° C., an alarm is sent in time.

[0039]When the heated air is fed into the molding cavity, the heated air is pressurized by an air pump, and the air pump is electrically connected to a temperature sensor in the molding cavity to adjust the output power of the air pump by obtaining real-time temperature in the molding cavity, such that the temperature in the molding cavity is between 65° C. and 85° C.

[0040]For example, when the temperature sensor sensing a drop in temperature in the molding cavity, increasing the power of the air pump so as to increase the input flow of hot air to increase the temperature in the cavity; if there is a continuous temperature drop of less than 65° C., an alarm is triggered.

[0041]In a word, as driven by the air pump, the air filtered by the filtering cabin is heated in the heating cabin, and the heated air fed into the molding cavity to contact the PLA fiber tows in the molding cavity, so as to achieve the effect of molding the hollow filter rods of PLA fiber.

[0042]In addition, during the production of the PLA hollow filter rod, the molding cavity is provided with a camera and a sensor to timely check the feeding condition of the PLA fiber tows and to promptly trigger an alarm in case of abnormality.

[0043]It should be noted that the total denier of the PLA fiber tows to be fed in the molding cavity preferably ranges from 30000 d×2~33000 d×2 (equivalent to 60000~66000 d).

[0044]The effect of different hot air temperatures on the molding and production of the filter rod, as well as the physical indicators and appearance of the filter rod were investigated, and the results are as follows:

[0045]That is to say, with respect to the production of a pipe (hollow) filter rod with the PLA tows, when the total denier of the tows is below 26000 d×2 (i.e. 52000 denier), there may be poor production of a filter rod of bad roundness and low hardness; when the total denier of the tows is 30000 d×2~33000 d×2 (equivalent to 60000~66000 d), the production is normal, and both the parameters and appearance of the filter rod meet the requirement; when the total denier of tows is more than 35000 d×2 (i.e. 70000 denier), the production becomes worse, and the parameters of the filter rod becomes variable. Therefore, the PLA tows having a specification of 30000 d×2~33000 d×2 (equivalent to 60000~66000 d) are suitable for the production of the pipe (hollow) filter rod.

[0046]It is preferable that, the loosening is performed simultaneously with two strands of PLA tows, and the total denier of each strand of the PLA tows is in the range of 30000 D to 33000 D.

[0047]Moreover, a feeding hole for adding triacetin is provided on the molding cavity during the production of the hollow filter rod of PLA, since it is required to add triacetin to the PLA fiber tows to improve the molding effect.

[0048]When the PLA fiber tows are molded, the added amount of triacetin is in a range of 12%~16%.

[0049]The effect of different added amounts of triacetin on the molding and production of the filter rod, as well as the physical indicators and appearance of the filter rod were investigated, and the results are as follows:

[0050]That is to say, with respect to the production of the pipe (hollow) filter rod with the PLA tows, when the added amount of triacetin is below 10%, the production situation is acceptable, but there may be un-molded filter rods of low hardness after the molding; when the added amount of triacetin is 12%~16%, the production is normal, and the parameters and appearance of the filter rods meet the requirement; when the added amount of triacetin exceeds 18%, the production becomes worse, and the parameters of the filter rod becomes variable. Therefore, the added amount of triacetin of 12%~16% is suitable for the production of the pipe (hollow) filter rod of PLA.

[0051]The method for producing the hollow filter rod of PLA fiber according to the present invention, it heats the PLA fiber tows by means of hot air heating. The hollow filter rods of PLA fiber obtained after curing have good molding effect, proper regularity, and low pollution.

[0052]The above description are merely illustrative examples of the present disclosure and does not limit the scope of the present disclosure. Namely, any equivalent changes and modifications made in accordance with the teaching of the present disclosure remain within the scope of the present disclosure. Those skilled in the art would readily conceive of its embodiments of the present disclosure upon consideration of the description and practice of the disclosure herein. The present application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principle of the present disclosure and comprise the common general knowledge or conventional technical means in the technical art not described in the present disclosure. The Description and Examples are to be regarded exemplary only, and the scope and spirit of the present disclosure are defined by the claims.