Method For Preparing Cigarette Filter Of Cellulose Acetate Fibers

Patent No. US3882878 (titled "Method For Preparing Cigarette Filter Of Cellulose Acetate Fibers") was filed by Daicel on Aug 22, 1973. The application was issued on May 13, 1975.

'878 is related to the field of cigarette filter manufacturing, specifically addressing the need for improved plasticizers used in the production of cellulose acetate filters. The background highlights the importance of plasticizers in bonding cellulose acetate fibers to maintain filter shape and hardness, a crucial step before cutting the filter material into rods.

The underlying idea behind '878 is the use of 1,3-butylene glycol diesters (diacetate, dipropionate, or dibutyrate) as a plasticizer for cellulose acetate cigarette filters. The key insight is that these diesters provide a faster curing rate at room temperature compared to traditional plasticizers like triacetin or triethylene glycol diacetate, without negatively impacting the cigarette's flavor.

The claims of '878 focus on a method for preparing a cigarette filter comprising blooming a tow of cellulose acetate fibers, adding 1 to 20% by weight of a plasticizer that includes at least one of the specified 1,3-butylene glycol diesters, and then gathering the treated tow. The claims also specify the tow characteristics, such as having 5,000 to 100,000 continuous fibers and 10 to 30 crimps per 25 mm.

In practice, the method involves applying the 1,3-butylene glycol diester plasticizer to the bloomed cellulose acetate tow using a spray gun or wick, ensuring uniform distribution. The plasticizer partially dissolves the cellulose acetate fibers, creating bonds at contact points and imparting the desired hardness. The treated tow is then processed using standard filter rod making machinery, wrapped in paper, and cut into filter rods.

The differentiation from prior approaches lies in the faster curing time achieved with the 1,3-butylene glycol diesters. While other plasticizers require extended curing times or elevated temperatures, this invention allows for rapid hardening at room temperature, improving manufacturing efficiency. Furthermore, the use of these diesters is claimed to be odorless, non-toxic, and to not negatively impact the cigarette's flavor, addressing shortcomings of existing plasticizers.

How does this patent fit in bigger picture?

Technical Landscape

In the early 1970s when '878 was filed, cellulose acetate was a common material for cigarette filters, at a time when filter manufacturing typically involved applying a plasticizer to a tow of cellulose acetate fibers to impart the necessary hardness and structural integrity. Achieving a balance between filter hardness, curing time, and impact on cigarette flavor was a key consideration, when systems commonly relied on established plasticizers and curing processes.

Prosecution Position

The disclosed method addresses the problem of achieving a rapid curing rate in cellulose acetate cigarette filters without compromising the flavor of the cigarette. The solution involves incorporating a plasticizer containing a diester compound of 1,3-butylene glycol into the cellulose acetate fiber tow. This architectural shift enables the production of filters with sufficient hardness at room temperature within a shorter time frame compared to filters made with conventional plasticizers, while also maintaining a desirable flavor profile.

Claims

This patent contains zero claims, so there are no independent or dependent claims to analyze.

Key Claim Terms New

Definitions of key terms used in the patent claims.

Term (Source)	Support for Specification	Interpretation
Blooming a tow (Claim 1)	A cellulose acetate fiber tow of a filament denier of 4 and a total denier of 43,000 having 26 crimps per 25 mm of the tow length was bloomed and a diacetate of 1,3-butylene glycol diacetate or a mixture of equal amounts of said diacetate and another plasticizer was added in a prescribed amount to the bloomed cellulose acetate fiber tow by means of a plasticizer-applicator.	An initial step in preparing the cigarette filter, performed on a tow composed of cellulose acetate fibers.
Cellulose acetate fibers (Claim 1)	A plasticizer for a cigarette filter of cellulose acetate fibers dissolves partially cellulose acetate fibers where it contacts the fibers and bonds the dissolved fibers to one another at random points of contact to retain the spaces of a filter made from the fibers and to impart a suitable hardness to the fibers in the filter shape. In this invention, cellulose acetate fibers are used in the form of a tow obtained by gathering 5,000 to 100,000 continuous fibers having a size of 1 to 16 deniers.	Fibers made of cellulose acetate, used to form the cigarette filter.
Gathering the thus treated bloomed tow (Claim 1)	Then, the tow is fed to a filter rod maker and wrapped by means of a rice paper. Then, it was cut into a length of 102 mm.	The step of collecting or assembling the bloomed tow after it has been treated with the plasticizer.
Plasticizer comprising as an ingredient at least one member selected from diacetate, dipropionate and dibutyrate esters of 1,3-butylene glycol (Claim 1)	When a plasticizer containing as an ingredient a diester compound of 1,3-butylene glycol is employed according to this invention, a sufficient hardness can be imparted to rods at room temperature within a short time. Diester compounds of 1,3-butylene glycol to be used in this invention are compounds represented by the following general formula: CH3 R-COOCH2CH2CH-OCOR wherein R stands for a methyl, ethyl or butyl group, and these compounds can be used singly or in combination with other plasticizers.	A plasticizing agent that contains at least one of the specified esters of 1,3-butylene glycol, used to treat the bloomed tow.
Uniform crimps (Claim 4)	It is preferred that 10 to 30 uniform crimps are given to the tow per 25 mm of the tow length.	Consistent bends or waves in the tow fibers.

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US3882878

DAICEL

Application Number: US38908473
Filing Date: Aug 22, 1973
Publication Date: May 13, 1975
External Links: Slate, USPTO, Google Patents

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