Patent Grant
12104325
This application is the national phase entry of International Application No. PCT/CN2021/123491, filed on Oct. 13, 2021, which is based upon and claims priority to Chinese Patent Application No. 202110402704.1, filed on Apr. 14, 2021, the entire contents of which are incorporated herein by reference.
The present disclosure belongs to the technical field of cigarette paper manufacturing, and in particular relates to a preparation method of a heat-not-burn cigarette paper with boron nitride as a thermally-conductive filler.
A smoking temperature of a traditional cigarette is as high as 900° C., and many harmful substances are produced during the combustion and pyrolysis of a tobacco leaf or a tobacco material at a high temperature. Low-tar and low-hazard cigarettes are the trend of cigarette development, and heat-not-burn (HnB) cigarette products are new tobacco products in which a cigarette wick mainly composed of shredded tobacco only gets hot and does not burn when heated by a specific heat source (below 500° C.). In this technology, a temperature is generally controlled at 350° C. or lower by baking a specially-made “smoke bomb” with a heater, such that nicotine and aromatic substances in a tobacco can be released. In this way, the production of a large number of toxic and harmful substances due to tobacco combustion is avoided, while a taste of a tobacco can be retained. Therefore, HnB cigarette products are very suitable for smokers to use instead of traditional cigarettes by bringing some tobacco characteristic feelings to consumers, reducing the hazard of tobaccos.
When an ordinary cigarette paper is baked, the thermal conductivity is low, which is not conducive to the release of nicotine and aromatic substances in a cigarette wick. In addition, the instability at high temperature may lead to the release of other odors, affecting a taste of a cigarette.
Technical problem to be solved by the present disclosure: In order to overcome the deficiencies of the prior art, a heat-not-burn cigarette paper with boron nitride as a thermally-conductive filler and a preparation method thereof are provided. The cigarette paper has high thermal conductivity and prominent flame-retardant stability at high temperature, and a color of the cigarette paper remains basically unchanged at high temperature.
To solve the technical problem, the present disclosure adopts the following technical solution:
A preparation method of a heat-not-burn cigarette paper with boron nitride as a thermally-conductive filler is provided, including a conventional cigarette paper making process of preparation of a coarse pulp, milling with a filler, sizing and papermaking, pre-drying, surface coating, post-drying, and calendering to obtain a paper, where pulp preparation specifically includes:
In the present disclosure, the surface coating may refer to coating 1 to 3 parts by weight of polyacrylamide (PAM as an additive on a surface of a cigarette paper by roller coating using a coating machine.
In the present disclosure, the PVA may have a molecular weight ranging from 200 to 3000.
In the present disclosure, the boron nitride particles may have an average particle size of 12 μm to 16 μm.
The present disclosure further provides a pulp including boron nitride as a thermally-conductive filler for preparing a heat-not-burn cigarette paper, where a raw material formula of the pulp includes the following components in parts by weight: 0.05 to 0.1 part of potassium oleate, 0.1 to 0.2 part of PVA, 5 parts of water, 15 to 2.5 parts of a softwood pulp, 50 to 70 parts of a hardwood pulp, 1 to 15 parts of boron nitride, and 20 to 50 parts of calcium carbonate.
A conventional cigarette paper making process typically includes the following steps: pulp preparation, sizing and papermaking, pre-drying, surface coating, post-drying, and calendering to obtain a paper. Generally, calcium carbonate is added as a filler directly to a wood pulp to adjust the whiteness and toughness of a paper.
The present disclosure divides the pulp preparation step into two stages:
(1) Potassium oleate and PVA are added to a mixed wood pulp of a softwood pulp and a hardwood pulp in the preparation of the coarse pulp. Potassium oleate serves as a surfactant to stabilize the coarse pulp. The PVA can fully expand in the subsequent heating procedure to be intercepted together with boron nitride in gaps of a pulp fiber network structure, which can reduce paper defects and enhance paper strength.
(2) Boron nitride and calcium carbonate are added to the coarse pulp for milling to obtain the pulp. Hexagonal boron nitride (BN) belongs to the hexagonal crystal system and is the most stable crystal in terms of physical and chemical properties. Moreover, with a hexagonal layered structure similar to that of graphite, the boron nitride has the characteristics of high-temperature resistance and oxidation resistance. In addition, boron nitride can be used as a cooling filler for various electrical and electronic devices, which exhibits a thermal conductivity as high as 1 W/mK to 15 W/mK and meets the engineering requirements of miniaturization and light weight. The introduction of boron nitride into the cigarette paper can greatly improve the coefficient of thermal conductivity of the cigarette paper; and as boron nitride itself has a flame-retardant effect, the stability of the cigarette paper at a high temperature (500° C.) can be greatly improved.
In a process of introducing boron nitride into the cigarette paper, it is necessary to consider the sufficient dispersion and mixing between boron nitride particles and cigarette paper fibers. Unlike the traditional process in which a filler is directly added to a pulp, the present disclosure adopts milling with a filler, that is, when boron nitride and calcium carbonate are added to a pulp, a temperature is raised to 60° C., and the agents are added under stirring, such as to realize the micro-reorganization of the boron nitride particles with the cigarette paper fiber structure. Paper fibers swell under the action of high temperature, mechanical shearing, and physical and chemical reactions, increasing the plasticity; and boron nitride can be uniformly dispersed and fully incorporated into the fibers under such process conditions to form a stable structure, thereby improving the quality control in terms of improving a coefficient of thermal conductivity of the paper fibers.
In addition, PAM is added as an additive during the surface coating in the present disclosure. Some —CONH groups in PAM molecules are hydrolyzed to produce —COOH, which produces cross-linking bonds with trivalent aluminum ions, calcium ions, and the like in a paper sheet and attaches to a surface of a paper product, making the paper product have prominent water resistance.
Compared with the prior art, the present disclosure has the following beneficial effects.
(1) Compared with an ordinary paper sheet with only calcium carbonate as a filler, the present disclosure introduces boron nitride particles as a thermally-conductive filler, which effectively improves the stability of a cigarette paper by improving a coefficient of thermal conductivity of the paper. Boron nitride has a small particle size (with an average particle size of 12 μm to 16 μm) and thus can be used as a thermally-conductive filler in a thin-walled or paper product, enabling a high heat removal capacity.
(2) Boron nitride particles are white and thus can retain the original whiteness and transparency of the cigarette paper. Boron nitride has a higher thermal conductivity than a thermally-conductive filler such as a metal oxide, and thus a load level thereof can be maintained relatively low, thereby making a product cost low.
(3) in the milling stage, the coarse pulp is heated to 60° C., and the filler is added under stirring, such as to realize the micro-reorganization of the boron nitride particles with the cigarette paper fiber structure. Paper fibers swell under the action of high temperature, mechanical shearing, and physical and chemical reactions, increasing the plasticity; and boron nitride can be uniformly dispersed and fully incorporated into the fibers under such process conditions to form a stable structure, thereby improving the quality control in terms of improving a coefficient of thermal conductivity of the paper fibers.
(4) The burning performance of the cigarette paper is adjusted, such that a burning rate of the cigarette paper is adapted to a burning rate of shredded tobacco, which is especially suitable for heat-not-burn cigarettes.
The present disclosure will be further described in detail below in conjunction with specific examples. The examples enable those skilled in the art to understand the present disclosure more comprehensively, but do not limit the present disclosure in any way.
A preparation method of a heat-not-burn cigarette paper with boron nitride as a thermally-conductive filler is provided, including the following steps:
The above steps (3) to (4) and (6) to (7) can be conducted according to methods and parameters of the conventional cigarette paper making process, which are not particularly limited in the present disclosure.
Relevant data of Examples 1 to 3 are shown in Table 1 (data in the table indicate the parts by weight of a corresponding component):
The heat-not-burn cigarette paper was baked at 300° C. for 5 min in a box-type resistance furnace, during which the degree of discoloration was observed.
A cigarette paper processing technology of the control group is different from that of Example 1 only in that no boron nitride particles are added.
The present disclosure has been described in detail herein and specific embodiments of the present disclosure are illustrated through examples in the example section. Various modifications and replacements can also be made to the present disclosure. However, it should be understood that the present disclosure is not limited to the specific forms disclosed herein. On the contrary, the present disclosure covers all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202110402704.1 | Apr 2021 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2021/123491 | 10/13/2021 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2022/217870 | 10/20/2022 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5849153 | Ishino et al. | Dec 1998 | A |
| 20180291561 | Kitagawa | Oct 2018 | A1 |
| 20210045433 | Osawa | Feb 2021 | A1 |
| Number | Date | Country |
|---|---|---|
| 109680540 | Apr 2019 | CN |
| 110629583 | Dec 2019 | CN |
| 111549562 | Aug 2020 | CN |
| 113152145 | Jul 2021 | CN |
| Number | Date | Country | |
|---|---|---|---|
| 20230265615 A1 | Aug 2023 | US |
