Self-Releasing Urethane Molding Systems - American Chemical Society

13 Self-Releasing Urethane Molding Systems: Productivity Study Downloaded via UNIV OF CALIFORNIA SANTA BARBARA on July 13, 2018 at 01:16:00 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

LOUIS W. MEYER The Dow Chemical Company, Freeport, TX 77541 This review identifies the primary reason for utilizing self-releasing urethane molding systems: increased productivity. In achieving this goal, however, the practical issues of various performance features, which may be critical to overall results, must be recognized, understood, and dealt with. For example, the need to paint parts is most often a very real and critcal issue which must be effectively worked out when using self-releasing systems. Theory relates release in terms of the equations defining adhesion, especially work of adhesion, Wa. What is sought is minimum adhesion and this is achieved by an IMR agent acting as a low energy film barrier between the mold metal high energy surface and the moderate (polar) energy surface of the urethane system itself. To date self-releasing systems have not provided infinite cycles of release, yet the number of consecutive releases for molds of differing degrees of complexities result in significantly improved productivity - the range being between 25% to 140% increased production yield. Cost reductions in manufacturing operations using IMR systems should be coupled to productivity increases. Typically, a 50% increase in productivity should show a cost reduction on the order of between 15% and 20%. The technology of self-releasing systems based on IMR agents is both new and incomplete in total development. Probably much needs to be done in terms of refinement and further extension of use, yet the overall benefits of a system which can be termed "effective" are of considerable practical value, even now. 0097-6156/85/0270-0195$06.00/0 © 1985 American Chemical Society

Kresta; Reaction Injection Molding ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

REACTION INJECTION MOLDING

196 Mold

release

requirement parts

cannot

release

by in

fact

the

press one

that in

need

urethanes, are

to

the

who

molding

effective

in

operation

spray

apply

a

cost

as

external

and

this

example, if

seconds

in to

it

This

is

turn

is

$.05

release

a 120

would

productivity

of

mold and a p p l i c a t i o n of

the

of

mold during sprays

total four

leads

"time-out" out

is

condition of

1 hour 12.5%

loss

the

with

productivity

The

possible

by

polyurethane least, The

the

surrounding

sprays.

the

derived

problems

from of

internal

mold r e l e a s e

agents

1.

Increased

Reduced manufacturing

3.

Improve of

which

akin are

production

loss

to

12.5%

of

37.5%

are

directly

to

is

further

not

always in

mold r e l e a s e

external

release based

agent or

in at

methods. The on

effective

efficiency, cost,

production

use

made

eliminating,

and r e a l .

system

the

system,

are:

optimizing

and

go down.

quality.

a d d s up

lost

it

ignored.

inherent

way o f

distinct

a self-releasing

2.

part

an i n t e r n a l

cuts

this

Optimization.

while

certainly

a possible

If

variables

Production

every

additional

again,

costs

A self-releasing

of

as

typical,

costs

on

use

necessitating

time.

increases,

quality,

are

c a n be r e a l i z e d

benefits

All

part

way,

and sprays

This

a total

even

cleaning

excessive

often

is

in

observe

Combining t h i s

important

of

30

spot

waxes

c a n n o t be e a s i l y

two

productivity.

reduction

operational

and m a n u f a c t u r i n g

incorporation

which

a 25%

common.

in

to time,

requires

devoted to

loss.

results

that

chemicals offers

minimizing

gains

loss

section

mold r e l e a s e

curtailed

which

not

cycle

conditions,

shift,

is

required in

it

backs.

use

addition,

more

When p r o d u c t i v i t y

a quantitive

time

is

draw

Its

be done as

process

hour

a value

subject

problems

external

each 8 25%

every

available production

between these

the

in

mold b u i l d - u p may h a v e t o

mold a

release In

molds

between

uncommon t o

time

external

make t h e

the

a spray

cycle, not

cycle.

is

to

overcoming

done by

The

agent,

of

composition,

of

numerous

in

of about

normally

efficiency

is

because

a shift

efficiency

related.

identified of

of

overall,

in

to

has

part.

machine u t i l i z a t i o n

relationship

discussed

once

previous

Production indirectly

This

otherwise

out

represent

The

"dirty"

up.

is

reflected

production

although

a portion

time

to

mold c l e a n hours,

losses

the

it

It

aid

brought

stick

and w a s t e f u l .

release

seat

the

achieving release

wasted

be o b s e r v e d .

to

effective

apply an e x t e r n a l

form of

second molding

higher the

to

the but

Is

s u c h as

chemical

like

molded

without

compounds i s

This

per

negatively

in

is

critical RIM

without

their

method of

apply an e x t e r n a l

productivity

in

b o t h messy

much as

spray

tools

common p r a c t i c e s

surface.

technical sense,

-

For

The

urethane

mold

of

and

process.

tools

urethanes

formed.

applies

The

their

because

Thus,

cycles.

molding

mold r e l e a s e

problem of

agent

without

their

molding

foam molded a r t i c l e s

for

nature.

articles

operator

or

been an important

urethane

Likewise,

The

"sticking"

release

of

c a n n o t be removed f r o m

adhesive which

have always type

be removed f r o m

agents.

the

are

any

agents*

cushions, such

agents of

performance.


13.

Self-Releasing Urethane Molding Systems

MEYER Commercial

IMR P r o d u c t s

It

that

appears

agent

the f i r s t

came a b o u t

defined

this

product

have

deleterious

been

limited

the introduction

through

which

commercial

is

effects

agent

products

-

release

on t i n c a t a l y s t s . t h e amount

and adding a t h i r d this

is

of an e f f e c t i v e

of a product

dimethylsiloxane

an e f f e c t i v e

to increasing

the system,

Systems

commercial promotion

through

as a c a r b o x y - f u n c t i o n a l

Although

of

and Self-Releasing

197

of

-

it

Practical

is

to

i n the B-side equipment

The i n t r o d u c t i o n

has to d a t e ,

prone

use has thus

to the process

Introduced.

a s IMR a g e n t s

fluid (1)·

agent,

tin catalyst

stream

IMR

chemically

of

other

n o t been

evident. In

an abstract

approached an a l l the

polyurea

system

gleaned, show

of an unpublished

the question

from

the u t i l i z a t i o n

fluid

which

A which

is

added

the

aromatic

quasi-prepolymers

I.

Chain

+

system

based

and Sobieski

(3).

They

dimethylsiloxane

i n conjunction

with a

Extender

Isocyanates

IMR a g e n t w h e n

for Internal

Amine

Type

Modified

Aromatic

Mold Release

Mondur

Tin

Fomrez

^Trademark

of Rubicon

^Trademark

of A i r Products

5Trademark

of Witco

(Reproduced w i t h

Chemical Chemical

(2)

permission

(5)

Index

PF

(3)

(4)

1.03

191 LF-179

33LV UL-28

0.10% 0.15%

Company Company

Chemical

Company

Company from R e f . 4.

Copyright

M

(PBW)

18-24 (1)

I .

(4)

Company

Chemical

Chemical

System

100

Dabco

o f Mobay

"Table

Quantity

Rubinate

o f Upjohn

in

Designation

Amine

^Trademark

andmolded

XA-10888.00L Isonate

prepolymers

^Trademark

shown

DETDA

Amine

Quasi-

Catalysts

is

to

with

(DETDA) a n d

exceptional process systems

polyol

formulated

diethyltoluendiamine

The formulated

Generic

IMR-II

o n a n amine m o d i f i e d

demonstrated

Formulation

Item Polyol

operation

amine c h a i n e x t e n d e r

attributes.

Table

I n f o r m a t i o n may b e

of Plevyak

a proprietary

MDI

product

a r e not a v a i l a b l e on e i t h e r

Further

the carboxy-functional

process

(2)

by making use of

a l l polyurea.

self-releasing had been

p a p e r , Dominquez

mold r e l e a s e

Specifics

employed. t h e work

of

i n a two s t r e a m

system

internal

system.

o r IMR a g e n t

however,

of

1983, SPI.)



198 Particular

attributes

characteristics; catalyst

reactivity,

exception which

release

had no

In

to

crucial

formulated the

the

chemicals should

are

It

of

Polyol

is

the

nature

of

limits

the

that

Reactivity:

In

added

incorporated

in

the

induce the

about

this

stream

a

remain

separate

third a

IMR

overall

molds

or

of

which

are

fully these

value

or

worthiness

mandatory

B-side

that

the

who

are

(polyols

an

the

active

which

are

isocyanates.

active IMR

the

agent

Obviously,

those

toward

the

IMR

components

isocyanate.

with

that

and c h e m i c a l l y w i t h

compounds t o

molding

components.

it's

in

agent

not

operation

important

seriously

problem on

this to

is

of

tin

IMR ln

a

totally

catalysts

the

to

make c e r t a i n

reduced.

IMR Not

catalyst,

always the

equipment

r e a c h the

operation,

but

agent all

IMR

fluids

way o f or

IMR

this

the

use

agent.

a n d IMR

head.

to

minimizing

catalyst

catalyst

For

tend

through

of

also

some d o .

Is

the

Is that

true)

mixing

free

are

If

A possible

not

either

the

they

stream

By

agent

Ideally,

"catalyst

k i l l "

preferable.

Bleed-Out: in

the

Freedom from e x u d a t i o n

molded a r t i c l e

is

also

or

bleed-out

be a c r i t i c a l

of

factor

performance. pheonomena, if

and p a i n t ,

for

however,

this

in

example, w i l l undesirable

Raw m a t e r i a l

compounds w h i c h polymer

present

Adhesive qualities

tape

avoided.

the

a

compound h a v i n g

degrading e f f e c t .

part,

have

the

stream

is

this

until

self-evident.

IMR

of

of

review

means

B-side

B-side

stream

two

agent

This be

This

Α-side

products

addition

remains

Exudation

metal

features

and o f t e n

physically

either the

other

carboxy-functional dimethylsiloxane

adding

problem

for

whole.

system.

or

problem (although

however,

tin

form.

the

reactivity

to

a

chemically inert

a two to

compounds

the

desirable

their

catalytic

third

stable

importantly,

parts

A brief

highly

choice

and s t a b l e

are

as

is,

compatible

example,

RIM

assessing

isocyanates with

supply

this

to

and i s o c y a n a t e manufactures

normally

and most

and u s e f u l n e s s

system

urethane

technology

bring

there

system.

important

be c o m p a t i b l e w i t h

hydrogen,

se,

be c o m p a t i b l e , b o t h

non-reactive,

of

per

chain extenders),

reactive

a n d 300

outstanding

retention,

coat.

adaptability

self-releasing

agents

plus

b e t w e e n 25

self-releasing

Compatibility; IMR

nucleation,

wax b a s e

release to

characteristics of

example, these

Features

addition

often

for

physical properties

stable

-

prior

Performance

include,

stable

are

solubility

to

molded p a r t , materials

be v e r y

feature

manufactures either;

the

(1)

will

poor.

will

s u c h as For

the

most

c a n be c o n t r o l l e d usually

select

which

are

free

or

only

isocyanate reactive,

characteristics

usually scotch

of

or

those (2)

this

problem.


13. MEYER


Physical should

Property

urethane

polymer.

plasticization usually

evident

that

There

IMR a g e n t s

is

most

must

often

IMR-II were

Table

in flexural

seen

Is

shown

through

i n "Table

essentially

property

II.

Physical

Property

Plasticization

a significant These

-

reduction

data f o r three low results

by the a d d i t i o n

non-existant

show

of the release

a good

indication

of

Without

C

Β

A

100 p t s

and

(4)

Amine

Amine

Conventional

+

Modified

Modified IMR-II

DETDA,

pts

21

18

18

Mondur

PF 1.03

53

60

60

28,650

30,000

30,800

3,600

2,800

2,900

265

280

290

280

480

490

Index,

is

while

Comparison o f Systems W i t h

Formulation Polyol,

either

modulus,

I I " ·

systems

of the

stability.

IMR

Type

of

i n molded p a r t s .

Comparative p h y s i c a l property

RIM s y s t e m s

product

properties

be no e v i d e n c e

changes i n p h y s i c a l p r o p e r t i e s

agent

in self-releasing

the the physical

by a r e d u c t i o n

elongation.

modulus

affect

or embrittlement

embrittlement in

Retention:

not adversly

199

pts

Property Flexural Tensile

Modulus, Modulus,

psi psi

Elongation, % Tear

Strength,

Heat

Sag,in.250°F/

60

p l i

min.

6

i n . overhang

0.57

0.51

0.53

4

i n . overhang

-

0.29

0.31

Specific

Gravity,

(Reproduced with

g/cc permission

Many RIM f o r m u l a t e d or

other

thermal

kinds

this

This

is

is

done,

expected.

Therefore, toughness

about

words

andincrease

The r e d u c t i o n ,

however,

should

by f u r t h e r

t h e bond s t r e n g t h lowered

plus

not bring

between f i b e r

formulation

Β of "Table

II"

1/16

inch milled

fiber

the f l e x u r a l

and

the reduction i n "Table

glass

in

fibers, linear

rigidity.

always

evident.

n o t be d r a s t i c . in a

additional

formulated

loss

in elongation. andpolymer

IMR a g e n t s .

was m o d i f i e d

i n e l o n g a t i o n was o n l y

is

IMR a g e n t

reduction

by the presence of

glass

part

should

about

when

shown

milled

i n elongation

system

1983, SPI.)

a reduction

some r e d u c t i o n

as evidenced

critically

Copyright

Incorporate

any combination of f i l l e r

self-releasing

be

also

to bring

expansion andc o n t r a c t i o n ,

When

other

from R e f . 4.

systems

of f i l l e r s

1.02

1.00

1.01

in In

should not

For example,

b y a 10% a d d i t i o n

modulus slightly

nearly more

of

doubled,

than

III".


30% a s

200


Table

III.

Effect

of

IMR

Plus

Milled

Physical Formulation Glass Neat

Loading* Flexural

Flexural Tensile,

Heat

psi

psi

Β

C 10 30,800

54,200

53,800

2,750

2,800

198

200

511

532

%

(250°F/60 min),

Reinforcement

10

pli Sag

Fiber

30,000

psi

Elongation, Tear,

Modulus,

Modulus,

Glass

in.

6

inches

overhang

0.30

0.20

4

Inches

overhang

0.25

0.21

1.09

1.11

Specific *737

Gravity,

A A Owens

parallel

to

Likewise,

when

the

by

loss

low

of

Most for

cost,

realizable

such as system

air

or

structure

or

The

concern.

the or

modified

by

RRIM

10% m i l l e d

remained i n t a c t , of

These

tear

as

are

glass

evidenced

strength -

results

or

Poor

a

also

good

shown

in

by

incorporating of

to

part

w h i c h makes

either

with

a blowing

therefore, stability

these

a

gas

agent

not

in

affect

nucleated froth:

emulsified

-

of

(paint).

problems

eyes, to

It

phenomenon o f the

the

it

of

the

the

must

the

brings

wet-out

is

(molded p a r t

difficulties

of

the

a liquid the

solid X

on

the

surface

of

those

liquids.

•

yields

value

of Y

to

the

sc.

the

a liquid

be r e l a t e d agents;

in

which

is

e y e , and orange

to

the

and of

(thus

the

well.

surface liquid will

wet

this liquid

to

plot

to

it surface

vapor

liquids

surface value

surface

spontaneously

usually

various

the

not

related

C5)

an e m p i r i c a l parameter the

of

peel

the

critical

against

such

and

when a l i q u i d

c o n t a c t angle of

of

possess

of

and co-workers as

one

a d h e s i o n as

property

occur

question the

to

wet-out

paint

to

is

terms

great

fish

he d e f i n e d This

of

poor

Zisman

c o s i n e of

solid

must

IMR

surface),

tend

Extrapolation se,

are

spread on a s u r f a c e

property

by p l o t t i n g

to

related

of to

always

about

lead

the

ability

described in

like

can usually

s p r e a d on a s u r f a c e .

effectively)

painting

p r e s e n c e of

can also

solid

Wet-out

of

and the

effectively

0°)

the

density

and improved

structure

agent must, the

are nucleated.

reduced

by n u c l e a t l o n ,

stability

wet-out

problems.

tension

as;

mold f i l l i n g ,

difficulties

relative

adhesion.

obtained

things

microcellular

hinder

fish

Painting

things

tension

of

A n IMR

elusive

orange p e e l ,

lv

of

system.

Painting:

The

properties

processed systems

such

achieved

nitrogen,

subtract

nucleated

paint

The is

formulation.

neither

RIM

include

increased ease

apppearance.

two

also

polymer

and r e t e n t i o n

urethane

this

benefits

as

C was

the

bond s t r e n g t h .

surface

cell

glass

III".

reasons

lower

of

elongation

retained

Nucleation: The

milled

formulation

toughness

of

"Table

1/16"

flow.

fiber, measure

g/cc

Corning

on

Properties

tension COS

s

tension

s p r e a d on


that

1

13. MEYER


surface. Paint

An example of

problems,

surface

tension

surface

t e n s i o n \f s c o f

For surface value

of

the

the by

coating. will

ο lv

of

part,

This

(1)

by

IMR

the

agent.

T y p i c a l methods

degreasing, Paint

post of

less

the

than

molded

tension,

were

free

Figure the

critical

part. agent

also

making i t

of

the

the

cure)

to

the

part

to

paint

power wash s y s t e m s

the the

surface one of

two

formulation

surface,

or

(2)

remove r e s i d u a l

cleaning include;

on

lowers less

IMR

c a n be s o l v e d by e i t h e r

solvent

1.

vapor

a n IMR

solvent

that

by

surface wiping,

which u t i l i z e

by s o l v e n t or

bleed of

"bite",

IMR vapor

both

out,

a topic

a solvent

of

wet-out,

previously

solvent

system

for

a paint

eliminate,

minimize

this

paint

adhesion deficiency.

topic

further

d i s c u s s e d under

the

or,

section

at

IMR

Obviously,

formulation

to

of

also

reviewed.

order

type

is

a n d ' p o s t molded freedom from

addressed in

is

in

liquid

cleaners.

selection

properly

of

or

the

self-releasing,

adhesion although a factor

controlled exudation

it

shown

presence of

surface

if

agent on

(after

and water

and e m u l s i o n

of

is

when

near

the

however,

addition

the

part

are

systems

problem,

solubilize

occur

surface

than

washing

the

the

critical

paint,

the

to

w h i c h makes i t

solid's the

relationship

tend

paints

self-releasing of

wettable ways:

this

therefore

201

the

must

very

Some o f

titled

be

least, this

Theoretical

Considerations· From the

ease

Finding to

of

the

foregoing

by w h i c h

each

IMR

agents

a compound w h i c h

provide

the

impossible.

Each

formulation of

property

-

suppliers

Theoretical

of

is

to

it

thus 1.

is

system

must

into is

obvious

only

that

curtailed.

any and a l l

perhaps

have i t s

accomplished

raw m a t e r i a l

quite greatly

systems

realistically

own

"right"

by a l i m i t e d

number

chemicals.

Considerations

sticks

to

doesn't the

be a c h i e v e d ,

urethane

self-release

far

urethane

When a m o l d e d p a r t that

so

it

selected is

c a n be "dumped" of

and e v e r y

a task

topics,

are

systems

release,

mold)

is

a d h e s i o n must

there

are

-

ability

the

one of

four

essential

adhesion.

be p r e v e n t e d . factors

which

problem (the Thus,

For

if

fact

release

most

molded

can affect

adhesion,

release: Wetting

(5)

The

of

the

liquid

polymer

to

"wet"

the

degree

the

mold · 2.

Spreading liquid

3.

Of

-

liquid

Complete "wetting";

spreads

Covalent Bonding the

4.

(5-6)

polymer

-

(7_)

system

to

in

Bonding

the

Hydrogen Bonding

(8)

-

polar

the

mold

these

polymer

to

phenomena,

spreading,

a n d two

bonding.

The

two

adhesion,

are

best

two are

are

"wetting" mold

ease

or

mold.

by d i r e c t

chemical

reaction

surface.

Bonding

by a s s o c i a t i o n of

the

highly

surface.

physical

chemical

the the

-

in

nature

-

wetting

and

c o v a l e n t bonding and hydrogen

broad c h a r a c t e r i s t i c s ,

p h y s i c a l and

chemical

examined s e p a r a t e l y .


of


202

of Various Liquids on A Specific Solid

Figure 1. Method to determine the c r i t i c a l surface tension of solids.


13. MEYER

When a l i q u i d a

material

c l e a n mold and c o n t a c t s

mentioned

all

easily

plate,

or

of

metallic Not

with which

the

wetting

s p r e a d i n g of

level at

(a

of

the

initial

thickness)

metal/liquid

now e s t a b l i s h e d reactive

to

direct

altered

or

In being this

the

film

interface promotes

which about

new f i l m

chemicals,

The

of

forces.

In

those

direct

s e p a r a t i o n Fs (9)

Is

by

are

in

imperfections.

the

very

alter

These

characteristics

interface,

the

part,

the

is

chemical

adhesion to

bonding

the

ease

are

of

longer

form a p h y s i c a l

essentially

the

system.

impervious In

the

low,

a point

I.e.

brought

however,

wetting

not

system

only

(10). of

adhesion/release are

bond.

referred they In

the

variables

as

any e v e n t ,

bond

of

of

that

the

two

force d.

of

related

about

that

work

Taylor is

this

is,

of

factors;

separation

only

because

are

secondary valence be p r i m a r y ,

separation

force

condition,

to

can also

be a f u n c t i o n

of and

also

1% o f

the

geometrical by

"Equation

1":

(1)

showed

of

this

that

e q u a t i o n was made b y K r a u s

for

release passed through

Under

a

and s p r e a d i n g

(.01)

refinement They

of

a c t as

d Further

to

addition

non-reactive with

the

of

release.

agents is

no

-

point

well. for

that

a bond

film

cure

agents,

practical fact

Wa

=

to

which

however, to

physical

molecular

characteristics

a

d i s t a n c e of

h a v e shown

complicated

Fs

shown

and the

a nearly

ease

complete

be

release

chemical

of

they

usually

many c a s e s ,

a d h e s i o n Wa,

surfaces

and are

point

energy the

and s p r e a d i n g must

that

chemicals of

as

high but

so

chemically

system

the

to

nickle

wetting

mold r e l e a s e

they

are

"wet",

to

reduce

enters

urethane

aluminum,

adhesive

at

to

liquid

adhesion via

to

an a i d

responsible

intermolecular,

Rutzler

is

but

the

of

energy is

Internal

forces

of

are

liquid

bond

barrier,

properties

Thus,

interface),

barrier

minimum v a l u e . physical

excellent

external

the

thus

these

occurs

controlled

( a new f i l m by

With

then

properties

and i n s t e a d

"wet"

to

system

previously

compounds t e n d

they

easily

"spreads"

interface.

bring

general,

barrier

the

because

they

the

The

steel,

substantially

otherwise

detriment,

wetting

and i n d i r e c t .

non-sticking,

be t h e y

are

of

polar

an optimum c o n d i t i o n

chemistry,

maximized both

in

high

surfaces, only

all

develop.

fairly

metal molds,

surface materials.

a r e a c t i v e urethane

surfaces,

quickly

which are

"wet"

other

like

its

adhesive forces

chemicals, very

203


thin

layer

and Mansar

adhesive systems

a maximum v a l u e w h e r e

Fmax *

the 1.46

force Fs.

condition: Fmax =

1.46

Wa

(2)

(.01)

d Direct

measurements

summarized by K r a u s s reasonable shown energy

later

accuracy in

systems

on

the

for

"Equation where

work

(11).

systems 3".

of

Values

of

free

The

Fmax e x i s t s

a d h e s i o n Wa h a v e a l s o Wa a r e of

direct

separation has

also

been

calculatable

chemical

bond

distance d for

been estimated

high

by McKelvey


with

as

is

204


(12)

a t about

4°A. Estimation

conditon

to c a l c u l a t e Fs

probably

on the order

solid-liquig 300

systems

ergs/cm ,

condition oxide

d for

of 20A°

of

high in

the values

be

nearly

on

the order

of

30 t o 50 e r g s / c m

of

the force

of

separation

adhesion,

yield

Case

1.

these

High

energy

(300)

release. =

30

a

is

(Case 2)

increased, the

thus

Young -

Wa - T t e

both

factor

good

0.00150

10

= Y lv

χ

surface

dynes/cm

8

dynes/cm

8

2

which

is

surface,

also no mold

2

a mold

release

has been a l t e r e d

to that

bond i n t e r m o l e c u l a r

contribute

equation

liquid

for

t o a much l o w e r

high

through

energy

of

distance release

the use of

surfaces.

It

-

wetting

surface

factor

3 to 4,

( C O S JS2£

t o 4 ) Ylv

to the

(degree of

complete wetting)

(6)

also

and that

+ Ylv

to 4) + 2

=

showed t h a t ^

by Harkins

the liquid-vapor 1.0).

tension

the l i q u i d

solid

factor

The studies

about

(3

(3)

vapor

spreading

exceeds

(3

(Good

release)

By making u s e of

energy

factors

always

approach zero Wa -

adhesion,

o f Bangham a n d Rozouk

of

10

( 1 + COS # )

3 8

v a l u e , Τ Γ e >-0.

thatlTe

1.095 χ

to low energy

• contact angle of

+ COS 0 )

work

no mold r e l e a s e .

w i t h mold r e l e a s e ,

and the high

(5)

* e

a

-

o f Wa u s e d a r e c o n f i r m a b l e

Ylv

+

#

The

i . e .

follows:

Ylv

Ylv(l

(.01)

f t

significant.

Dupree

Wa a s

where,

value,

Calculation

8

the high

The values

relates

tension

energy.

(OH)

surfaces, can

good a d h e s i o n and poor

surface,

equivalent

(Poor

low energy s u r f a c e ,

value.

functional

2.17 p s i

difference

agent

under metal

°

£.01) -

20x10"

The

two c a s e s ,

energy surface

approximately

=

surface

surface

200 t o

1,588 p s i

2. High

Fs

of

of

o r more

low energy

is

release))

4x10

Case

hydroxyl

these

energy

example, with

Wa f o r

(metallic)

poor

(1.46)

-

high

systems

for

for

results;

adhesion, Fmax -

as f o r

hand,

as low as the l i q u i d

interface

F o r many h i g h

a s 400 e r g s / c m ,

hydrogen bonding, On t h e o t h e r

film

The range

o f Wa a r e o n t h e o r d e r

conjunction with

systems.

different

possible.

to 100°A.

a n d c a n be as h i g h

surface

liquid

of

are also

Ylv

e always has

and co-workers

surface

tension

the contact angle

This (1 +

(8)

tended

by a to

being so: COS^O (5

to

6)


showed

13.

MEYER

If

Ylv

Self-Releasing Urethane Molding Systems Is

Further, one be

say

if

Which has

the

mold s u r f a c e

(1

for

generally

show

effective

been

to

this way

materials about

as

metal,

360

but

ergs/cm . 2

rather

spreading

them,

some l o w

a low

factor

i.e.

they

characteristic at

surface

are

energy

e

systems,

then

Assuming

to

would

this of

in

a

of

very

plastics;

tension is

These

sc

less

near,


a d h e s i o n as

free

Materials

types

value

are

also

and p o l y p r o p y l e n e .

value

of

surfaces.

which

are

urethanes

surface

that

lv

work

systems,

different

polyethylene,

the

energy

self-releasing.

three

tension

low

urethane

relative

least

dynes/cm.

for

energy materials,

have a d e f i n e d c r i t i c a l

30

vapor

relationship

observed that of

include

all

urethane is

to

(4)

polytetrafluoroethylene,

liquid

not

example, the

Dupree

surface

from adhering

than

is

Wa =• 3 0 0

C0S#)

+

Young -

on the

which

then

therefore:

is

cured

dynes/cm,

oleflnic

=Vlv

Wa

It

the

instead, zero,

60

205

the

IMR

g i v e n by E q u a t i o n

4

follows:

Vlv

Wa -

(1

+

) = Vlv

0 2

=

30

the

value used

The

problems

are

similar.

Kaelble

ergs/cm in

of

provides

of

the

ionic

isocyanate,

not

too

or

other

Thus,

to

surfaces

a be

possible

metal

-

likely, or

minimize

by an I n t e r f a c e

adhesion,

present.

Production Increased

or It

which

In

terms

metal

an e x t e r n a l of

adhesion the

not

of

only

are

physical chemical

non-reactive

and the

whether

this

(EMR)

mold r e l e a s e

mold

as the

releasibility,

mold r e l e a s e

hydroxyl

polyol.

a reactive

non-polar,

mold s u r f a c e

an i n t e r n a l

avoids

of

therefore,

such

polyurethane Is

achieved

agent,

(IMR)

.

the

metal

such

A

bonding,

and/or

materials

which

a non-wetable,

film.

with

by

(40-80)

chemical

chain extender

chemical

those

about

directly

standpoint

shown

hydrogen bonding with

makes no d i f f e r e n c e

of

incorporation

but

i.e.,

between the

application

the

of

modes of

be p r o t e c t e d f r o m p o l a r

layer

boundry

via

bonding

have been

layer

hydroxide

or

eliminate

as w e l l ,

boundry

two

either

polyurethanes nature

2.

hydroxide

of

of

Case

mold s u r f a c e s

functions must

problems

metal

have a s u r f a c e

Such a surface reaction

example of

Typical to

(J)

the

adhesion viewed from a chemical

or

must by

though

the the

agent.

Optimization efficiency

reduced

If

gains

shorter

molding

automatically

are cycle

follows

starts to

with

b e made

the in

place

molding c y c l e .

production

is

the

as

a consequence

where of

It

optimization this

must

optimization. is,

starts.

increased


be A What


206

productivity economic part

-

-

the y i e l d

factor,

the q u a l i t y

Cycle

Efficiency:

which

should

cycle

is

ta

-

ts

T h e number

better

by cost surface

reduction

-

appearance

the

of

of

consecutive self-releasing

the

cycles

to reach a p r a c t i c a l yet e f f i c i e n t

calculable.

+

followed

often,

factor.

be a t t a i n e d

readily

to -

factor,

a n d , most

This

may b e d o n e b y t h e

molding

"Equation;

ts

(5)

η where:

ta -

average cycle

to

original

-

ts

time

s

required

η = number

of

release This

cycle

time

molding

required

system shonw

consecutive cycle

the relationship t a , which

a n IMR a g e n t i n Figure

releases

as c a n be seen

mold r e l e a s e

spray,

between e x t e r n a l

is

mold

ts,

for

between

2.

derived

in

the

from a

self-releasing

between t a and η only

to dramatically

"Table

averaged

as a b e n e f i t

η consecutive

Typically,

a r e needed

the

obtained by e l i m i n a t i n g

A generalized relationship

graphically

releases,

e

to apply external

t o a p p l y EMR s p r a y

cycles.

η consecutive

(n l),

spray.

cycle

containing

molding

for

time,

consecutive release

equation expresses

effective

time

about

is

10

improve

the molding

IV".

T a b l e I V . R e l a t i o n s h i p o f the Average C y c l e Time f o r η C o n s e c u t i v e R e l e a s e s t a , and the Number o f R e l e a s e s Between E x t e r n a l Mold Release Spray η TIME

(SECONDS) Releases

Time

In

η

to

ts

ta

120

30

120.0

1

120

30

93.0

10

120

30

90.3

100

120

30

90.0

O O

a paper by T a y l o r

(13), e t .

a l . this

been extended to r e f l e c t

productivity

manner.

efficiency

answer for

Increased

to improved p r o d u c t i v i t y ,

wanting

systems

system which would is η

cycle

a valid releases

containing provide

but d i f f i c u l t

Between

Spray

(Sec.)

type

alone,

yet it

is

IMR a g e n t s .

an i n f i n i t e

target.

of

relationship

improvements however,

is

has

similar

n o t the whole

fundamental

to

Ideally,

self-releasing

numbers

On a more

in a

of

a

the

releases

(n -

practical level,

b e t w e e n 30 a n d 3 0 0 a r e a t t a i n a b l e .


reason ©o)

however


MEYER

ω >

I

I

I

η Consecutive Releases

Figure 2 . Averaged cycle time for η consecutive releases obtained as a result of eliminating the time necessary to apply external mold release spray.



208

Productivity; system is

is

The

a function

and

primary

reason for

increased productivity. of

three

scrap rate.

reduction

In

factors:

the

terms

% Cycle

Reduction »

100

Its

cycle

of

a

self-releasing

simplest

time,

Equation

and p e r c e n t p r o d u c t i v i t y

r e d u c t i o n may b e e x p r e s s e d a s

wanting

In

5

form

machine the

i n c r e a s e as

productivity

utilization,

percent

cycle

a result

of

the

cycle

follows:

to-ta

(6)

to % Productivity

Increase

(Cycle

Basis

Only)

=

100

(to-ta)

(7)

ta Using

the

% Cycle

cycle

times

Reduction =

% Productivity To

this these

trial gain

Increase

utilization combined

of

Table

= 33%

gain,

increased provide

and of

effects

(60.5%)

is

productivity

to

a RIM

Table V .

be a d d e d

reduced as

Scrap,

(8

is

t a b u l a t e d In


sec. 75

hr

shift)

"Table is

V"·

self-releasing

results

production The

t y p i c a l of

total

the

system can

operation.

IMR

With

(6/8

Shift)

87.5

IMR 90

22.5

M

Shift)

2 123,480

%

+60.5

shifts/day

different

6 d a y s / w e e k ; 45 w e e k s / y e a r

commercial

might

question

industrial

confidentiality characterization "Table

(7/8

35.0

76,950

This

in

improved

actual

120

%

designs?

shown

It

process manufacturing

How m u c h p r o d u c t i v i t y

actual

of

The

5

Increase, hr

gains

scrap rate.

significant.

%

Parts/year,

*Two 8

only).

the

Features

Utilization, Parts/Hr

100,

d e t e r m i n e d by an e x t e n s i v e

Without Time,

value η -

F a s c i a P r o d u c t i v i t y w i t h and Without an IMR Agent

Productivity Cycle

the

(machine basis

must

f a s c i a manufacture

realized

1 for

25% a n d ,

productivity

machine of

of

was

molds

be e x p e c t e d under

both

molds

only.

a wide

laboratory

production conditons.

the

from

range of

a n s w e r e d by e v a l u a t i n g a number

used are

A summary

To

identified tabulation

conditions,

maintain by of

tool of and

account

group these

trials

VI".


is

13. MEYER

Table V I . Generic

209


System

P r o d u c t i o n Performance

Summary

Components: Polyol-Amine M o d i f i e d + Chain

Extender

Isocyanate Molds :

F a s c i a or

Description

-

-

IMR-II

DETDA

Quasi

Prepolymer

Fascia-like

Simple

Complex

Complex

iront

Rear

Front

150

150-180

200-275

240-300

85-95

85-90

150-200

100-200

325+*

160

186+*

100

125

Mold Original

Results

Simple

Cycle,

Rear

sec. New C y c l e , No.

of

w/o

sec.

cycles

EMR

Best

case

Worst

case

50 25

25

Cycle Reduction,

%

Best

43

50

38

58

Worst

37

43

25

33

Best

76

100

38

140

Worst

58

76

33

50

Production Increase,

%

*Run s t o p p e d end p o i n t

External -

as

m o l d r e l e a s e was

little

as

once

every

25

cycle

efficiency.

ranged range Cost

was

cycles.

from 50%

a worst

to

75%

Reduction:

automatically

in

For

300 a l l ,

this

case

determined.

s t i l l

every

All

not

n e c e s s a r y , but

cycles not

of

33%

to

increases,

possible

a reasonable idea

One a p p r a o c h

unit

cost

With

reasonable assumptions part

volumes, be

Assumed

this

weight,

values

raw m a t e r i a l

140%,

the

reduced

in

cost,

a simplfied cost,

for

production increase versus

cost

The

following

is

and r e l a t e

this

sensitvity

inverse

by

on such t h i n g s

tooling study

Weight

Urethane Tooling Annual

=

=

might equating way. as

and p r o d u c t i o n reduction can

used

to

relationship:

lbs $1.00/lb

$250,000

Production

Variable Fixed

=8.90

System

Costs

Costs

=

-

200,000

= Raw M a t e r i a l (1.2)

(Initial

units costs

+

Variable

Tooling

can't

is

Basis: Part

the

should

it

cost

c a n b e made

inputs

in

answer

of

costs

with

reduction

obtained,

basic

often

once

be a f a c t o r

are

what

so

significant.

cost

question

as

improvements

figures

economic of

of

are

every

often

A l t h o u g h an exact

b o t h v a r i a b l e and f i x e d

determined.

illustrate

to

accounting

be.

molded

case

values

how m u c h ?

actual

to

a best

As

By

as

enough to

The

productivity

only

or

productivity

being t y p i c a l .

follow.

get

so,

often

series,

be g i v e n u n l e s s to

or

Costs

Costs)



210 Cost

Equation:

Total

Cost

-

Variable

Unit

Cost

+ Fixed

Unit

(8)

Cost

Unit

Therefore: Total

Initial =

Costs

$8.90

+

200,000

=» $ 1 0 . 1 5 Employing cost

the

this value

initial of

production

"Table

VII".

VII.

$12.18

unit

percent

percent

Table

+

+

$250,000

Unit

Unit

increase

=

cost

cost

1.2

$

(8.90

+

1.25)

Units $22.33 as

a base value

reduction

for

c a n be d e t e r m i n e d .

Economic S e n s i t i v i t y Cost

Study:

of

given

manufacturing values

These

Production

of

are

shown

Increase

vs.

Reduction

Production

Raw

Tooling

Fixed

Total

Cost

Increase

Material

Amount

Cost

Cost

Reduction

(%)

$/Unit

$/Unit

$/Unit

$/Unit

(%)

0

8.90

1.25

12.18

22.33

0

25

8.90

1.00

9.74

19.64

12.0

50

8.90

.83

8.12

17.85

20.0

75

8.90

.71

6.96

16.57

25.8

100

8.90

.63

6.09

15.62

30.0

150

8.90

.50

4.87

14.27

36.1

A

separate

RIM

study

based

IMR

a n d RIM

without

benefits,

"Table

reduction

in

effects which

of

is

capital

with

VIII".

cycle

these

on

In

IMR this

investment showed

particular

yielded costs

requiremnts

similar

increased productivity

benefits

in

cost

example, a

by 63%.

saving

on

The the

comparing

savings 27% combined order

significant.


of

17%,

13.

Table V I I I .

C a p i t a l Investment Economic Comparison o f RIM Without IMR v s . RIM w i t h IMR

Process/Product Unit

Weight

Unit

Thickness

RIM

(#)

Raw M a t e r i a l Cycle

(In.)

($/#)

(Min.)

Parts/Hour Operating

Hours

R I M + IMfe

7.00

7.00

0.150

0.150

1.00

1.00

2.50

1.83

24.00

34.7

6,000

6,000

Clamps Capacity

Utilization

Efficiency Scrap

Production

Capital

Equipt.

(Units)

2

0.90

0.90

0.75

0.87

5

2

184,680

301,380

($M)

950

Costs Raw

2

(%)

Actual

$M/YR

225

$M/YR

$/Unit 7.00 .22

1.23

Variable

225

.75

8.41

Costs*

2,000

7.97

10.82

M f g . Costs

*Estimated due

+63

.18

Tooling

Total

-27

7.00

Utilities

% Change

950

$/Unit

Material

Fixed

211


MEYER

2,400

7.96

19.23

15.93

-17

a t $ 2 , 0 0 0 M / Y R f o r R I M a n d $ 2 , 0 0 0 + 20% f o r R I M + IMR

to Increased

labor.

Conclusions Self-releasing typically

systems

conjunction with 20%

should dealt This

and

with

this

increase,

by about a cost

IMR a g e n t s c a n

50% t o 7 5 % .

reduction

In

o f b e t w e e n 12% t o

problems

such as the need

to paint

molded p a r t s , c a n

i n a r e a l i s t i c way.

product

commercial

improving

on " e f f e c t i v e "

be e x p e c t e d .

Practical be

based

increase productivity

technology although quite

introduction,

the value

of

s t i l l

holds

t h e RIM p r o c e s s

new i n b o t h d e v e l o p m e n t

great

promise

in

radically

Itself.

Literature Cited 1. J . E. Plevyak, L. A. Sobieski, Proceedings of the ACS Division of Polymeric Materials Science and Engineering, Vol. 49, p. 619-624 (1983). 2. R. G. Dominquez, SPE NATEC '83 Conference Proceedings, p. 52. 3. J . E. Plevyak, L. A. Sobieski, Proceedings of the SPI - 6th International Technical/Marketing Conference, p. 365-369 (1983). 4. L. W. Meyer, Proceedings of the SPI - 6th International Technical/Marketing Conference, p. 372 (1983). 5. W. A. Zisman, "Adhesion and Cohesion", P. Weiss Ed. Elsevier Amsterdam, 1982.



212

6. D. H. Bangham, R. I. Razouk, Trans. Faraday Soc V. 33, 805, (1937). 7. D. H. Kaelble, "Physical Chemistry of Adhesion"; Wiley Interscience, New York, NY (1971). 8. W. D. Harkins, "The Physical Chemistry of Surfaces", Reinhold, New York, (1952). 9. D. Tayler and J. Rutzler, "Industrial Engineering Chemistry", 50, 904 (1958). 10. G. Kraus and J . Manson, "Journal of Polymer Science", 6, 625 (1951); 8, 448 (1952). 11. G. Kraus, "Adhesion and Adhesives", John Wiley, p. 45 (1954). 12. J . McKelvey, "Polymer Processing", John Wiley, p. 161 (1962). 13. R. Taylor, Proceeding of the ACS Division of Polymeric Materials Science and Engineering Vol. 49 p. 625 (1983). RECEIVED October 5, 1984


Self-Releasing Urethane Molding Systems - American Chemical Society

Recommend Documents