According to an aspect of the invention, there is provided a process for producing a dye-containing negative curable composition, the process including passing a mixture containing a dye, a photopolymerization initiator, and a radical polymerizable monomer through a filter having a pore diameter of from not less than 0. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the nucleic acid sequences as well as methods for producing and using the polypeptides. The vacuum chamber is evacuated by an evacuating means, and a reactive gas is introduced thereto by a gas introducing means. An electrically powered first motor operates via a linkage to rotate the levers about the first axes and to move the pinch rolls between open positions spaced from the product, and closed positions contacting and gripping the product therebetween. With the side handle mounted in front of the collar, easier access to the adjusting collar and easier reading of the collar settings is achieved.