GB1594651A - Book binding method - Google Patents

Description

(54) BOOK BINDING METHOD (71) We, THE RESEARCH ASSOCIA TION FOR THE PAPER AND BOARD PRINTING AND PACKAGING INDUSTRIES, a body corporate organised under the laws of the United Kingdom, and of Randalls Road, Leatherhead, Surrey, KT22 7RU, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to a method of binding books and to books produced according to the method.

Conventional sewn books have a rounded spine to improve the qualities of the book including its appearance. Such a book is produced by sewing together sections, applying a thin layer of water based adhesive along the spine, allowing the adhesive to dry, then rounding and backing the spine to serve as a basis for the covered book. On the other hand, a hardcased, unsewn book is produced by bonding the pages of a block with adhesive and then rounding and backing the block to provide the basis for a covered book having the appearance of a traditionally sewn book. Millions of books have been made by this method using a cold disper sion adhesive. The main advantage of the latter type of book is that the unsewn binding speeds up production of the book block compared to sewing and costs are therefore reduced.

It is generally accepted that unsewn binding with hot melt adhesives is faster and cheaper than with cold dispersion adhesives. Whilst hot melt adhesives may therefore be used to reduce costs even further, cold dispersion adhesives are preferred because they give a stronger and more durable binding over a wider range of papers.

Moreover, there are difficulties associated with rounding and backing a book when using hot melt adhesives and in producing a book in which the rounded shape is retained for a reasonable proportion of its life. These diffi culties can be attributed to a lack of control over the heat applied when a hot melt adhesive is reheated prior to rounding and backing.

Conventional reheating techniques make use of infrared heating, hot plating and the use of heated formers. All of these techniques suffer from the disadvantage that hot melt adhesive has a low heat conductivity and it is, therefore, very difficult to apply sufficient heat in the short space of time necessitated by high speed production. Another disadvantage is that a temperature gradient is produced through the adhesive layer, with the highest temperature and less viscous adhesive on the outside of the spine. When pressure is applied, there is then a tendency for the adhesive to penetrate into and through the linen, rather than into the edge of the book.

The present invention seeks to overcome these problems in a method of book binding comprising the steps of applying dielectric heating to soften a hot melt adhesive, applied to the spine of an unsewn book, and then rounding and backing said spine.

The dielectric heating is preferably effected by means of radio frequency heating equipment such as that normally used for drying or reducing the moisture content of the body to be heated. However, microwave heating may also be feasible. In any case, the object is to produce heat internally within the layer of hot melt adhesive rather than on its outer surface.

Dielectric heating may be effected remote from a rounding and backing machine. For example, unsewn books with a layer of hot melt adhesive applied to the spine may be transported on a belt over radio frequency electrodes, the speed of the belt being such that the layer of ahesive is softened sufficiently for the subsequent rounding and backing of the spine. The transportation of the books on such a belt also has the advantage of spreading the heat through the adhesive layer when the spine of the book passes over spaced radio frequency electrodes. Alternatively, the dielectric heating may be effected within a specially constructed rounding and backing machine.

With regard to the use of radio frequency dielectric heating, this is the first time, to our knowledge, that it has been proposed as a form of reheating a hot melt adhesive applied to the spine of an unsewn book to soften the adhesive prior to rounding and backing. Besides the advantage of speed, as mentioned above, radio frequency dielectric heating can be used with standard hot melt adhesives, such as those which would normally be available to a book binder. Such adhesives include Croda Polymers 36610 and 36-35600; Borden Cascomelt; and National Instantflex 59 and 50. The heat generated within the hot melt adhesive is a function of the frequency and applied voltage and also of a property of the material (i.e. the loss factor).The generation of heat by the use of radio frequency dielectric heating apparatus is easily controllable in that heating ceases immediately the current is turned off and heating begins at the same input when the current is turned on. This lends itself ideally to book production especially compared with the techniques which employ hot plates or ceramic infrared radiators which are heated by gas or electricity.

In the book binding method according to the invention, the hot melt adhesive should preferably be of a material and applied in a layer to the spine of the book such that the layer will substantially recover its original shape quickly after the book is flexed, for example, by opening the pages. The hot melt adhesive preferably contains a high percentage (e.g.

30%-90% by weight) of ethyl vinyl acetate (copolymers and/or resins), or an ethyl vinyl acetate with a high (18%-50% by weight) content of vinyl acetate to obtain good heat generation. Some other polymers used in adhesives will react similarly.

In a preferred embodiment of the method according to the invention a strip of stretchable material is suitably applied to the layer of hot melt adhesive when applied to the spine of a book. Such a strip of material may be a strip of expandable linen, or of expandable creped paper, (which is cheaper than linen). The bound pages can then be transferred, at any time after the adhesive is cold, to a machine where radio frequency dielectric heating is employed to reheat and thereby soften the adhesive prior to rounding and backing.

Typically, the spine of the book is heated to 60"-800c in 10-25 seconds by a radio frequency of about 28MHz (e.g. + 0.1 MHz). It was possible to obtain a greater heating effect in a shorter time by reducing the radio frequency but this requires more current which may be a limiting factor with regard to the mass production of books which are heated one after the other. The current required, for one book at a radio frequency of approximately 28.1 MHz, was 0.08-0.10 amps.

The invention will become more apparent with regard to the following description taken in conjunction with the attached drawings, in which: Figure 1 is a perspective view of RF heating apparatus, and Figures 2 and 3 show books bound according to the method of the invention.

In our preliminary experiments, a radio frequency dielectric heater was used which worked on the stray field system, in which, with reference to Figure 1, a series of electrodes of alternating polarity (shown instantaneously by + -) form a platen 1. The electrodes 1 extend transversely of the direction of movement 2 of a belt 3 made of material which is substantially unaffected by, and which does not substantially affect, the radiated radio frequency energy. Books 4 are guided by strings 5 as they are transported on belt 3 in the direction of movement 2. The belt speed is such that with a particular radio frequency and current, a layer of hot melt adhesive on the spine 6 of each book is softened enough to round and back the book when transferred to a (known) rounding and backing machine.As first used, the radio frequency apparatus was tuned to a frequency suitable for drying water based coatings or adhesives.

Initially, sample discs approximately 0.5mm thick of a range of hot melt adhesives, ethyl vinyl acetate copolymers and resins were prepared and passed over the electrode system.

The apparatus was tuned by altering the frequency until a heating effect was obtained. It was found essential for the samples to be very close to the electrodes, and this was achieved by weighting them down with a non-reactive material. It was also found that the frequency required to heat the materials was lower than that set on the apparatus for drying off water.

The temperatures reached by the various materials could be controlled by adjustment of belt speed, i.e. time of exposure and also by varying the frequency.

Ethyl vinyl acetate copolymers are available in many grades distinguished by the percentage of vinyl acetate and the melt flow index. They are included in the formulation of most hot melt bookbinding adhesives. Grades containing 18, 28, 33 and 40% by weight vinyl acetate were passed through the heater at the same frequency and exposure time settings. It was found that the heating effect increased with a percentage of vinyl acetate.

Samples of three tackifying resins namely, Hercures AR No. 100, Pentalyn (Regi:stered Trade Mark) C and Imprez (Registered Trade Mark) 100 were also heated by this method.

Seventeen hot melt adhesives were also heated by this method. The temperatures reached varied from adhesives to adhesive and were lower than those obtained for any of the grades of ethyl vinyl acetate adhesives for an equivalent frequency and exposure time setting. However, by lowering the frequency very slightly the heat produced in the adhesives could be increased greatly and their softening temperatures could be reached.

When testing unsewn books, five different adhesives were used. These adhesives were selected with regard to the characteristics that the adhesive layer should recover its original shape well and quickly after flexing, and that the adhesive should contain a fairly high percentage of EVA, or an EVA with a high vinyl acetate content.

In the rounding and backing trials, twenty books were bound, using the same paper, on a Sulby Auto Minabinder using each adhesive, without altering any settings. The paper used (of antique wove type) was known to be in commercial use for rounded and backed hot melt books. The books were trimmed to a size of 185mm. x 131.Smm and were all 30 mm thick. It was found that after the books had been passed through the heater they could be pushed into a round against a fore edge forme, by hand. This meant that it was possible to mount a forme below the jaws of a hand operated Marshall backing press, thus giving even clamping.

The temperature of the various adhesives after passage through the heater varied, as obviously did the flexibility of the adhesive at a particular temperature. It was found that by making minor adjustments to the frequency and belt speed of the heater a suitable result could be obtained for each adhesive.

The temperatures o the book spines as taken from the heater ranged between 600 C 76"C and this was achieved for heating times of 12-23 seconds. It was possible to obtain a greater heating effect in a shorter time, by lowering the frequency of operation. This meant that more current was absorbed from the heater. The amount of current which can be taken is a limiting factor on the apparatus and would have to be considered if a line of books was being heated at one time. The current taken by one book at a frequency of approximately 28.1 MHz was 0.08 to 0.10 amperes.

It was found advisable to cool the spines after backing, by means of a cold air blast, before the clamp was released. If this was not done the convex round produced in the clamp tended to distort.

Well shaped spines could be produced, the main hazard being the tendency of the adhe sives to be squeezed through the line, or out at the top and bottom of the spine. This could be partly overcome on the hand operated backing press by gradually increasing the arc described by the roller, and by slowing up its operation.

Further books were made using the same binder settings as before but using four diff erent papers and only one of the adhesives.

Including the paper already used the five types were as follows: Wt. of book Caliper g/m2 (grams) A Antique Wove 0.185mm 109 422 B Offset Cartridge 0.113mm 87 546 C Newsprint 0.106mm 50.5 307 D M.F.Printing 0.102mm 81 545 E Offset Cartridge 0.119mm 88 530 All the books were 185 x 131.5 mm, except books made with paper C which were 177 x 118.5 mm. Paper D gave the most trouble with adhesive bursting through the linen. It was found easier to round and back books on softer, more compressible papers. The pressure and action of the backing roller and the tem perature of the spine were less crucial, less force was required and there was no tendency for the adhesive to be squeezed through the linen.

To test the use of short and long grain papers, blocks were made of papers B, C, D, F and one adhesive. Half were bound long grain and half cross grain. The blocks were radio frequency heated before rounding and backing.

No significant differences were found in the ease of rounding and backing with either grain direction.

Handling and storage trials were made with sample books of each paper and adhesive combination. The object of the trials was to store books in various ways and to observe any deterioration with time. The books to be assessed for general rigidity, loss of round and evenness at the top of the spine and fore edge, and sag. Books stored on shelves were supported on boards adhered to the front and back outside pages against the shoulder. The boards were mounted flush with the top of the block but overlapping by a small amount at the bottom.

To test for shelf storage with handling, the books were placed upright on a shelf. At intervals the books were examined and then opened at at least ten places before being replaced on the shelf.

To test for shelf storage without handling, the books bound with adhesives 2, 3,4 and 5 listed above all on paper A were placed upright on a shelf. The books were not opened at all.

In Figure 2, the left hand book represents one which was opened and the right hand book one which was not opened in the above tests.

To test blocks stored flat and unopened, the blocks bound with adhesives 2, 3, 4 and 5 listed above all on paper A were piled flat and left undisturbed, see Figure 3.

Results of storage trials. The reference letter denotes the paper, the reference number denotes the adhesive.

Shelf storage with handling during a three month period. Rigidity: Al, A5, C6 produced the firmest books, and the rest were satisfactory.

Sag: Sag was slight in all cases, in no books did the fore edge sag down to the shelf.

First examination for round retention: Before opening A4 and C6 had lost the most round.

After opening all the books went out of shape but there was some recovery during the first two minutes after closing the book. A2, A6, D6 and E6 had the best round retention.

Further openings resulted in loss of most of the round in all cases, and the spines became somewhat uneven. D6 and E6 retained the best shapes.

Shelf storage without handling, during a 7 week period. There was some loss of round and sag in all cases, but less than occurred in the case of the opened books. The spines retained an even curve although it was reduced.

Blocks stored flat and unopened, during a 7 week period. There was virtually no loss of round in these blocks.

Effect of section folds on round retention.

Three sewn books were bound with adhesive 6 on paper B for direction comparsion with unsewn books B6. This was done to ascertain whether the presence of folded sections during rounding and backing produced a more permanent round than cut pages.

It was found that during shelf trials the sewn books were slightly more prone to sag than the unsewn books, but that the sewn books were more rigid to handle. After opening, the unsewn books retained slightly more round at first, but after more handling there was little difference between the two types. The sewn books however kept a more even appearance at the spine although almost all the round had been lost.

The adhesives used in the test above were: 1. Croda36610 2. Borden Cascomelt Ref: A 3. Borden Cascomelt Ref: B 4. Croda 36-35600 5. National Instantflex 59 6. National Instantflex 50 WHAT WE CLAIM IS: 1. A method of bookbinding comprising the steps of applying dielectric heating to soften a hot melt adhesive, applied to the spine of an unsewn book, and then rounding and backing said spine.

2. A method according to claim 1 in which the dielectric heating is carried out with radio frequency heating equipment.

3. A method according to claim 1 in which the dielectric heating is microwave heating.

4. A method according to claim 2 in which the hot melt adhesive contains 30%-90% by weight of ethyl vinyl acetate.

5. A method according to claim 2 wherein the hot melt adhesive is principally an ethyl vinyl acetate with 18%-50% by weight content of vinyl acetate.

6. A method according to any one of claims 1,2 or 4,5 wherein the spine of the book is heated to 600--800C prior to rounding and backing.

.7. A method according to claim 6 wherein the heating occurs within 10-15 seconds with a radio frequency of about 28 MHz.

8. A method according to any one of claims 1,2 or 4-7 wherein a strip of stretchable material is previously appleid to a layer of said hot melt adhesive on the spine of the book, the book being transferred, when the adehsive is cold, to a binding machine where dielectric radio frequency heating is employed to reheat and soften the adhesive prior to said rounding and backing.

9. A method according to claim 8 wherein the unsewn books with said layer of hot melt adhesive applied to the spine are transported on a belt over radio frequency electrodes, the speed of the belt being such that the layer of adhesive is softened sufficiently for the subsequent rounding and backing of the spine.

10. A method according to any one of claims 1-8 wherein the dielectric heating is effected within a rounding and backing machine.

11. A method of bookbinding substantially as herein described with reference to Figure 1 of the accompanying drawings.

12. A book bound according to the method of any one of the preceding claims.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (12)

**WARNING** start of CLMS field may overlap end of DESC **. round in these blocks. Effect of section folds on round retention. Three sewn books were bound with adhesive 6 on paper B for direction comparsion with unsewn books B6. This was done to ascertain whether the presence of folded sections during rounding and backing produced a more permanent round than cut pages. It was found that during shelf trials the sewn books were slightly more prone to sag than the unsewn books, but that the sewn books were more rigid to handle. After opening, the unsewn books retained slightly more round at first, but after more handling there was little difference between the two types. The sewn books however kept a more even appearance at the spine although almost all the round had been lost. The adhesives used in the test above were: 1. Croda36610 2. Borden Cascomelt Ref: A 3. Borden Cascomelt Ref: B 4. Croda 36-35600 5. National Instantflex 59 6. National Instantflex 50 WHAT WE CLAIM IS:

1. A method of bookbinding comprising the steps of applying dielectric heating to soften a hot melt adhesive, applied to the spine of an unsewn book, and then rounding and backing said spine.

2. A method according to claim 1 in which the dielectric heating is carried out with radio frequency heating equipment.

3. A method according to claim 1 in which the dielectric heating is microwave heating.

4. A method according to claim 2 in which the hot melt adhesive contains 30%-90% by weight of ethyl vinyl acetate.

5. A method according to claim 2 wherein the hot melt adhesive is principally an ethyl vinyl acetate with 18%-50% by weight content of vinyl acetate.

6. A method according to any one of claims 1,2 or 4,5 wherein the spine of the book is heated to 600--800C prior to rounding and backing.

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7. A method according to claim 6 wherein the heating occurs within 10-15 seconds with a radio frequency of about 28 MHz.

8. A method according to any one of claims 1,2 or 4-7 wherein a strip of stretchable material is previously appleid to a layer of said hot melt adhesive on the spine of the book, the book being transferred, when the adehsive is cold, to a binding machine where dielectric radio frequency heating is employed to reheat and soften the adhesive prior to said rounding and backing.

9. A method according to claim 8 wherein the unsewn books with said layer of hot melt adhesive applied to the spine are transported on a belt over radio frequency electrodes, the speed of the belt being such that the layer of adhesive is softened sufficiently for the subsequent rounding and backing of the spine.

10. A method according to any one of claims 1-8 wherein the dielectric heating is effected within a rounding and backing machine.

11. A method of bookbinding substantially as herein described with reference to Figure 1 of the accompanying drawings.

12. A book bound according to the method of any one of the preceding claims.